Question

Find the exact values under the given condition
cos(theta + beta)

sin theta = 3/5, lies in quad I,
sin beta = 5/13 lies in quad II

Any idea on how to do this?

Thanks

Answer 1

Now, can you find cos theta, and cos beta?

Answer 2

And then we use this formula:

cos(α + β) = cos(α)cos(β) – sin(α)sin(β)

Answer 3

cos 4/5*-12/13 - 5/13*3/15

= -63/65

Thanks!

Answer 4

You're welcome!

Answer 5

cos(α + β) = cos(α)cos(β) – sin(α)sin(β)

Answer 6

so now just find the cos theta and cos beta