Question

Hi! Can anyone help me out with this problem?

Find the exact value of the given quantity.

sin[2arccos(5/7)]

Answer 1

did you type it correctly?

Answer 2

5/7 seems weird

Answer 3

Yep that is what it is!

Answer 4

arccos is equal to cos^-1 right?

Answer 5

yup

Answer 6

kk

Answer 7

so, what does cos^-1 do?

Answer 8

Doesn't it give you the inverse?

Answer 9

Like y=cos^-1x is equal to x=cosy?

Answer 10

yea

Answer 11

so the first thing you do is the inside of this one, so you need to change out that arccos(5/7)

Answer 12

How do I do that? Do I plug into the calculator arccos(5/7)? I got 44

Answer 13

well you can, but looking at your special angle chart is useful too

Answer 14

also, you shouldn't get a whole number

Answer 15

When I'm looking at the special angle chart what am I looking for?

Answer 16

the angle that yields a cosine of 5/7