Trigonometry Examples

$\sec (- 90)$

Step 1

Rewrite $\sec (- 90)$ in terms of sines and cosines.

$\frac{1}{\cos (- 90)}$

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 third quadrant.

$\frac{1}{- \cos (90)}$

Step 3

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

$\frac{1}{- 0}$

Step 4

Multiply $- 1$ by $0$ .

$\frac{1}{0}$

Step 5

The expression contains a division by $0$ . The expression is undefined.

Undefined