Evaluate without using a calculator. Give answer in radians and degrees. Show work please or explain it!

Question

anonymous · Answer

$$\cos^{-1}(-\sqrt{2}/2) $$

dumbcow · Answer

from the unit circle i know that cos(x) = -sqrt(2)/2  when x = 3pi/4 and 5pi/4

dumbcow · Answer

convert to degrees.....pi = 180

dumbcow · Answer

do you need more explanation?

anonymous · Answer

thank you so its 180 degrees & 3 pi/4 ?

dumbcow · Answer

??
no pi radians is equivalent to 180 degrees

there are 2 possible answers (2 diff angles satisfy cos(x) = -sqrt2/2)
i gave you answers in radians, you have to convert to degrees by replacing pi with 180

dumbcow · Answer

good reference http://www.mathpeer.com/index.php?act=trigonometry&trig=radian_measure_and_the_circular_functions

anonymous · Answer

oh... i'm sorry so the answer is 180 degrees & pi ? I don't understand how to get to 180 degrees. :/

dumbcow · Answer

hmm ok apparently i am only confusing you more

just look at the unit circle and find -sqrt2/2, the answers will be the angle measures

anonymous · Answer

5 pi/4 ?

dumbcow · Answer

yep thats 1 answer

anonymous · Answer

i hope i'm not annoying or anything lol you don't have to help me but is the answer for $$\sin^{-1} (-1)$$ = 270 degrees, (3 pi/2) ?