Trigonometry Examples

$5 \cos (90) - 8 \sin (270)$

Step 1

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

$5 \cdot 0 - 8 \sin (270)$

Step 2

Multiply $5$ by $0$ .

$0 - 8 \sin (270)$

Step 3

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.

$0 - 8 (- \sin (90))$

Step 4

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

$0 - 8 (- 1 \cdot 1)$

Step 5

Multiply $- 8 (- 1 \cdot 1)$ .

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Step 5.1

Multiply $- 1$ by $1$ .

$0 - 8 \cdot - 1$

Step 5.2

Multiply $- 8$ by $- 1$ .

$0 + 8$

Step 6

Add $0$ and $8$ .

$8$