Question

Find the exact value of the expression using the provided information: cos A = -1/6 and cos B = -3/5 pi 13 years ago

Answer 1

Please explain, I'm lost on this one

Answer 2

Maybe using Sum or Difference Identity: cos(A+B) = cos A cos B - sin A sin B?

Answer 3

what is the question?

Answer 4

You say to find the exact value of the expression and then you don't give the expression.

Answer 5

sorry, cos(A+B)

Answer 6

cos(A+B)= cosAcosB-sinAsinB

Answer 7

That's as far as I've gotten I'm not sure on how to use the formula

Answer 8

You know that both A and B are 3rd quadrant angles. That is given. So the sin and cos of both angles must be negative.