Question

Use the reference angle to find the exact value of the expression.
cos13pi/4

Answer 1

o.o how is that even possible... can u explain what i have to do to figure this out...

Answer 2

I know the reference angle is pi/4, so then it would change to cos45 then I'm lost

Answer 3

cos13pi/4

13 π / 4 = 2π + π + 1/4 π

Answer 4

Agree or disagree or question?

Answer 5

Question

Answer 6

Post question.

Answer 7

I am trying to do this by steps so I am asking if you follow or agree with the first step. If you have a question, just post it as we go along.

Answer 8

I dont understand what your post is saying

Answer 9

We are finding the cosine of the angle 13pi/4.

When I do this type problem, I first figure out which quadrant the terminal side of the angle will fall so I can find the ref angle.

To find that, I divided 13 pi by 4 and got 3 and 1/4 pi.

Answer 10

Because we are doing trig on the unit circle and every 360 degrees (same as 2 pi radians), we end up where we started, I split up the angle as

13 π / 4 = 2π + π + 1/4 π and I am going to throw the 2π into the garbage can.

This angle is all we need: ( π + 1/4 π )