# Question 350ab

Jan 27, 2018

The answer is $- \frac{5}{4} \pi$ radians.

#### Explanation:

To convert degrees to radians, multiply the degree value by pi/(180º):

-225cancelº*pi/(180cancelº)#

$\frac{- 225 \pi}{180}$

$- \frac{5}{4} \pi = - 1.25 \pi \approx - 3.926$

Jan 27, 2018

$- \frac{5 \pi}{4}$

#### Explanation:

It's very worth memorizing all of the ${45}^{\circ}$ angles in radians, which become the $\frac{\pi}{4}$ angles.

${45}^{\circ} \to \frac{\pi}{4}$
${135}^{\circ} \to \frac{3 \pi}{4}$
${225}^{\circ} \to \frac{5 \pi}{4}$
${315}^{\circ} \to \frac{7 \pi}{4}$

Having these memorized tells you quickly that $- 225 \to - \frac{5 \pi}{4}$.

You can also convert any degree measure to radians by multiplying it by $\frac{\pi}{180}$.