Calculus Examples

$9 \cos (9 π)$

Step 1

Subtract full rotations of $2 π$ until the angle is greater than or equal to $0$ and less than $2 π$ .

$9 \cos (π)$

Step 2

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

$9 (- \cos (0))$

Step 3

The exact value of $\cos (0)$ is $1$ .

$9 (- 1 \cdot 1)$

Step 4

Multiply $9 (- 1 \cdot 1)$ .

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Step 4.1

Multiply $- 1$ by $1$ .

$9 \cdot - 1$

Step 4.2

Multiply $9$ by $- 1$ .

$- 9$