Trigonometry Examples

${(2 \cos (t) - 4 \sin (t))}^{2} + {(4 \cos (t) + 2 \sin (t))}^{2} = 20$

Step 1

Square both sides of the equation.

${({(2 \cos (t) - 4 \sin (t))}^{2} + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2

Simplify ${({(2 \cos (t) - 4 \sin (t))}^{2} + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2}$ .

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Step 2.1

Simplify each term.

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Step 2.1.1

Rewrite ${(2 \cos (t) - 4 \sin (t))}^{2}$ as $(2 \cos (t) - 4 \sin (t)) (2 \cos (t) - 4 \sin (t))$ .

${((2 \cos (t) - 4 \sin (t)) (2 \cos (t) - 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.2

Expand $(2 \cos (t) - 4 \sin (t)) (2 \cos (t) - 4 \sin (t))$ using the FOIL Method.

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Step 2.1.2.1

Apply the distributive property.

${(2 \cos (t) (2 \cos (t) - 4 \sin (t)) - 4 \sin (t) (2 \cos (t) - 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.2.2

Apply the distributive property.

${(2 \cos (t) (2 \cos (t)) + 2 \cos (t) (- 4 \sin (t)) - 4 \sin (t) (2 \cos (t) - 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.2.3

Apply the distributive property.

${(2 \cos (t) (2 \cos (t)) + 2 \cos (t) (- 4 \sin (t)) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3

Simplify and combine like terms.

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Step 2.1.3.1

Simplify each term.

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Step 2.1.3.1.1

Multiply $2 \cos (t) (2 \cos (t))$ .

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Step 2.1.3.1.1.1

Multiply $2$ by $2$ .

${(4 \cos (t) \cos (t) + 2 \cos (t) (- 4 \sin (t)) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.1.2

Raise $\cos (t)$ to the power of $1$ .

${(4 (\cos^{1} (t) \cos (t)) + 2 \cos (t) (- 4 \sin (t)) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.1.3

Raise $\cos (t)$ to the power of $1$ .

${(4 (\cos^{1} (t) \cos^{1} (t)) + 2 \cos (t) (- 4 \sin (t)) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.1.4

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

${(4 {\cos (t)}^{1 + 1} + 2 \cos (t) (- 4 \sin (t)) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.1.5

Add $1$ and $1$ .

${(4 \cos^{2} (t) + 2 \cos (t) (- 4 \sin (t)) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.2

Reorder $2 \cos (t)$ and $- 4 \sin (t)$ .

${(4 \cos^{2} (t) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.3

Add parentheses.

${(4 \cos^{2} (t) - 4 (\sin (t) (2 \cos (t))) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.4

Reorder $\sin (t)$ and $2$ .

${(4 \cos^{2} (t) - 4 (2 \cdot \sin (t) \cos (t)) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.5

Apply the sine double-angle identity.

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 \sin (t) (2 \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.6

Add parentheses.

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 (\sin (t) (2 \cos (t))) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.7

Reorder $\sin (t)$ and $2$ .

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 (2 \cdot \sin (t) \cos (t)) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.8

Apply the sine double-angle identity.

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 \sin (2 t) - 4 \sin (t) (- 4 \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.9

Multiply $- 4 \sin (t) (- 4 \sin (t))$ .

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Step 2.1.3.1.9.1

Multiply $- 4$ by $- 4$ .

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 \sin (2 t) + 16 \sin (t) \sin (t) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.9.2

Raise $\sin (t)$ to the power of $1$ .

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 \sin (2 t) + 16 (\sin^{1} (t) \sin (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.9.3

Raise $\sin (t)$ to the power of $1$ .

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 \sin (2 t) + 16 (\sin^{1} (t) \sin^{1} (t)) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.9.4

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 \sin (2 t) + 16 {\sin (t)}^{1 + 1} + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.1.9.5

Add $1$ and $1$ .

${(4 \cos^{2} (t) - 4 \sin (2 t) - 4 \sin (2 t) + 16 \sin^{2} (t) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.3.2

Subtract $4 \sin (2 t)$ from $- 4 \sin (2 t)$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + {(4 \cos (t) + 2 \sin (t))}^{2})}^{2} = {(20)}^{2}$

Step 2.1.4

Rewrite ${(4 \cos (t) + 2 \sin (t))}^{2}$ as $(4 \cos (t) + 2 \sin (t)) (4 \cos (t) + 2 \sin (t))$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + (4 \cos (t) + 2 \sin (t)) (4 \cos (t) + 2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.5

Expand $(4 \cos (t) + 2 \sin (t)) (4 \cos (t) + 2 \sin (t))$ using the FOIL Method.

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Step 2.1.5.1

Apply the distributive property.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 4 \cos (t) (4 \cos (t) + 2 \sin (t)) + 2 \sin (t) (4 \cos (t) + 2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.5.2

Apply the distributive property.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 4 \cos (t) (4 \cos (t)) + 4 \cos (t) (2 \sin (t)) + 2 \sin (t) (4 \cos (t) + 2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.5.3

Apply the distributive property.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 4 \cos (t) (4 \cos (t)) + 4 \cos (t) (2 \sin (t)) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6

Simplify and combine like terms.

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Step 2.1.6.1

Simplify each term.

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Step 2.1.6.1.1

Multiply $4 \cos (t) (4 \cos (t))$ .

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Step 2.1.6.1.1.1

Multiply $4$ by $4$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos (t) \cos (t) + 4 \cos (t) (2 \sin (t)) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.1.2

Raise $\cos (t)$ to the power of $1$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 (\cos^{1} (t) \cos (t)) + 4 \cos (t) (2 \sin (t)) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.1.3

Raise $\cos (t)$ to the power of $1$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 (\cos^{1} (t) \cos^{1} (t)) + 4 \cos (t) (2 \sin (t)) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.1.4

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 {\cos (t)}^{1 + 1} + 4 \cos (t) (2 \sin (t)) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.1.5

Add $1$ and $1$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \cos (t) (2 \sin (t)) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.2

Add parentheses.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 (\cos (t) (2 \sin (t))) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.3

Reorder $\cos (t)$ and $2 \sin (t)$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 (2 \sin (t) \cos (t)) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.4

Apply the sine double-angle identity.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 2 \sin (t) (4 \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.5

Reorder $2 \sin (t)$ and $4 \cos (t)$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 \cos (t) (2 \sin (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.6

Add parentheses.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 (\cos (t) (2 \sin (t))) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.7

Reorder $\cos (t)$ and $2 \sin (t)$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 (2 \sin (t) \cos (t)) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.8

Apply the sine double-angle identity.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 \sin (2 t) + 2 \sin (t) (2 \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.9

Multiply $2 \sin (t) (2 \sin (t))$ .

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Step 2.1.6.1.9.1

Multiply $2$ by $2$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 \sin (2 t) + 4 \sin (t) \sin (t))}^{2} = {(20)}^{2}$

Step 2.1.6.1.9.2

Raise $\sin (t)$ to the power of $1$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 \sin (2 t) + 4 (\sin^{1} (t) \sin (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.9.3

Raise $\sin (t)$ to the power of $1$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 \sin (2 t) + 4 (\sin^{1} (t) \sin^{1} (t)))}^{2} = {(20)}^{2}$

Step 2.1.6.1.9.4

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 \sin (2 t) + 4 {\sin (t)}^{1 + 1})}^{2} = {(20)}^{2}$

Step 2.1.6.1.9.5

Add $1$ and $1$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin (2 t) + 4 \sin (2 t) + 4 \sin^{2} (t))}^{2} = {(20)}^{2}$

Step 2.1.6.2

Add $4 \sin (2 t)$ and $4 \sin (2 t)$ .

${(4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 8 \sin (2 t) + 4 \sin^{2} (t))}^{2} = {(20)}^{2}$

Step 2.2

Simplify terms.

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Step 2.2.1

Combine the opposite terms in $4 \cos^{2} (t) - 8 \sin (2 t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 8 \sin (2 t) + 4 \sin^{2} (t)$ .

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Step 2.2.1.1

Add $- 8 \sin (2 t)$ and $8 \sin (2 t)$ .

${(4 \cos^{2} (t) + 0 + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin^{2} (t))}^{2} = {(20)}^{2}$

Step 2.2.1.2

Add $4 \cos^{2} (t)$ and $0$ .

${(4 \cos^{2} (t) + 16 \sin^{2} (t) + 16 \cos^{2} (t) + 4 \sin^{2} (t))}^{2} = {(20)}^{2}$

Step 2.2.2

Move $4 \sin^{2} (t)$ .

${(4 \cos^{2} (t) + 4 \sin^{2} (t) + 16 \sin^{2} (t) + 16 \cos^{2} (t))}^{2} = {(20)}^{2}$

Step 2.2.3

Factor $4$ out of $4 \cos^{2} (t)$ .

${(4 (\cos^{2} (t)) + 4 \sin^{2} (t) + 16 \sin^{2} (t) + 16 \cos^{2} (t))}^{2} = {(20)}^{2}$

Step 2.2.4

Factor $4$ out of $4 \sin^{2} (t)$ .

${(4 (\cos^{2} (t)) + 4 (\sin^{2} (t)) + 16 \sin^{2} (t) + 16 \cos^{2} (t))}^{2} = {(20)}^{2}$

Step 2.2.5

Factor $4$ out of $4 (\cos^{2} (t)) + 4 (\sin^{2} (t))$ .

${(4 (\cos^{2} (t) + \sin^{2} (t)) + 16 \sin^{2} (t) + 16 \cos^{2} (t))}^{2} = {(20)}^{2}$

Step 2.3

Rearrange terms.

${(4 (\sin^{2} (t) + \cos^{2} (t)) + 16 \sin^{2} (t) + 16 \cos^{2} (t))}^{2} = {(20)}^{2}$

Step 2.4

Apply pythagorean identity.

${(4 \cdot 1 + 16 \sin^{2} (t) + 16 \cos^{2} (t))}^{2} = {(20)}^{2}$

Step 2.5

Simplify with factoring out.

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Step 2.5.1

Factor $16$ out of $16 \sin^{2} (t)$ .

${(4 \cdot 1 + 16 (\sin^{2} (t)) + 16 \cos^{2} (t))}^{2} = {(20)}^{2}$

Step 2.5.2

Factor $16$ out of $16 \cos^{2} (t)$ .

${(4 \cdot 1 + 16 (\sin^{2} (t)) + 16 (\cos^{2} (t)))}^{2} = {(20)}^{2}$

Step 2.5.3

Factor $16$ out of $16 (\sin^{2} (t)) + 16 (\cos^{2} (t))$ .

${(4 \cdot 1 + 16 (\sin^{2} (t) + \cos^{2} (t)))}^{2} = {(20)}^{2}$

Step 2.6

Apply pythagorean identity.

${(4 \cdot 1 + 16 \cdot 1)}^{2} = {(20)}^{2}$

Step 2.7

Simplify terms.

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Step 2.7.1

Simplify each term.

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Step 2.7.1.1

Multiply $4$ by $1$ .

${(4 + 16 \cdot 1)}^{2} = {(20)}^{2}$

Step 2.7.1.2

Multiply $16$ by $1$ .

${(4 + 16)}^{2} = {(20)}^{2}$

Step 2.7.2

Simplify the expression.

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Step 2.7.2.1

Add $4$ and $16$ .

$20^{2} = {(20)}^{2}$

Step 2.7.2.2

Raise $20$ to the power of $2$ .

$400 = {(20)}^{2}$

Step 3

Raise $20$ to the power of $2$ .

$400 = 400$

Step 4

Since $400 = 400$ , the equation will always be true for any value of $t$ .

All real numbers

Step 5

The result can be shown in multiple forms.

All real numbers

Interval Notation:

$(- \infty, \infty)$