Trigonometry Examples

$\cos (90) + 3 \sin (270)$

Step 1

Simplify each term.

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Step 1.1

The exact value of $\cos (90)$ is $0$ .

$0 + 3 \sin (270)$

Step 1.2

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because sine is negative in the third quadrant.

$0 + 3 (- \sin (90))$

Step 1.3

The exact value of $\sin (90)$ is $1$ .

$0 + 3 (- 1 \cdot 1)$

Step 1.4

Multiply $3 (- 1 \cdot 1)$ .

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Step 1.4.1

Multiply $- 1$ by $1$ .

$0 + 3 \cdot - 1$

Step 1.4.2

Multiply $3$ by $- 1$ .

$0 - 3$

Step 2

Subtract $3$ from $0$ .

$- 3$