Trigonometry Examples

135 °

$135 °$

Step 1

Take the cosine of

135 °

$135 °$ .

\cos (135 °)

$\cos (135 °)$

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.

- \cos (45)

$- \cos (45)$

Step 3

The exact value of

\cos (45)

$\cos (45)$ is

\frac{\sqrt{2}}{2}

$\frac{\sqrt{2}}{2}$ .

- \frac{\sqrt{2}}{2}

$- \frac{\sqrt{2}}{2}$

Step 4

The result can be shown in multiple forms.

Exact Form:

- \frac{\sqrt{2}}{2}

$- \frac{\sqrt{2}}{2}$

Decimal Form:

- 0.70710678 \dots

$- 0.70710678 \dots$