Question

find exact value of cos-1(-square root2/2)
where do I start on this?

Answer 1

you could do it on your calculator, but you also know that the angle which gives a cosine ratio of -sqrt 2/2 is is 135 degrees, which also happens to be the answer.

Answer 2

it's cos-1( negative sq root/2). would this still equal 135 degrees?

Answer 3

135 degrees

Answer 4

my options are -pi/4, -3pi/4, pi/4, 3pi/4 which one of these would be 135 degrees?

Answer 5

3pi/4 = 135 degrees

Answer 6

would I just find that on the unit circle? thank you

Answer 7

yeah that's on the unit circle. also it's helpful to know that pi/2 is 90.. you can use this as a reference point to find other angles