felicia888
Find the exact value of the expression using the provided information: cos A = 1/6 and cos B = 3/5 pi<A<3pi/2 and pi<B<3pi/2



This Question is Closed

felicia888
Best Response
You've already chosen the best response.
0
Please explain, I'm lost on this one

felicia888
Best Response
You've already chosen the best response.
0
Maybe using Sum or Difference Identity: cos(A+B) = cos A cos B  sin A sin B?

chihiroasleaf
Best Response
You've already chosen the best response.
0
what is the question?

Mertsj
Best Response
You've already chosen the best response.
0
You say to find the exact value of the expression and then you don't give the expression.

felicia888
Best Response
You've already chosen the best response.
0
sorry, cos(A+B)

felicia888
Best Response
You've already chosen the best response.
0

Mertsj
Best Response
You've already chosen the best response.
0
cos(A+B)= cosAcosBsinAsinB

felicia888
Best Response
You've already chosen the best response.
0
That's as far as I've gotten I'm not sure on how to use the formula

Mertsj
Best Response
You've already chosen the best response.
0
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.

Mertsj
Best Response
You've already chosen the best response.
0
dw:1352460203985:dw

Mertsj
Best Response
You've already chosen the best response.
0
dw:1352460347694:dw

Mertsj
Best Response
You've already chosen the best response.
0
Use those values in the formula for cos (A+B)