I need help evaluating an expression under specific conditions

Evaluate the expression under the given conditions.tan(*θ* + http://www.webassign.net/images/phi.gif); cos *θ* = −1/3, *θ* in Quadrant III, sin http://www.webassign.net/images/phi.gif= 1/4, http://www.webassign.net/images/phi.gif in Quadrant 4

Copied from my math homework, I'm not getting the right answer.

Re: I need help evaluating an expression under specific conditions

Hey AKPunk49.

Can you show us what you tried: (Hint: did you try using the angle addition formulae?)?

Re: I need help evaluating an expression under specific conditions

can not possibly be in the fourth quadrant. Why?

Re: I need help evaluating an expression under specific conditions

Re: I need help evaluating an expression under specific conditions

It doesn't change the fact that can not possibly be positive in the fourth quadrant. In fact, I don't see anything different at all...

Re: I need help evaluating an expression under specific conditions

Oh my-lanta...its in Quad. 2. I'm having an odd week, sorry for that.

The book tells me to make two right triangles in the corresponding quads and then find the identities, which I did. Then I plugged it all into the addition formula for tangent. I got -sr8/3+1/4 all divided by 1-(-sr8/3)(1/4)

Sorry if that's confusing...

Re: I need help evaluating an expression under specific conditions

Quote:

Originally Posted by

**chiro** Hey AKPunk49.

Can you show us what you tried: (Hint: did you try using the angle addition formulae?)?

I did, I don't know if I'm not doing it correctly or if I just don't know how to properly reduce.

Re: I need help evaluating an expression under specific conditions

Hello, AKPunk49!

We are given: . in Quad 3.

. . Then: .

. .

We are given: .

. . Then: .

. .

We have: .

. . . . . . . . . . . . . . . .

Multiply by

Therefore: .

Re: I need help evaluating an expression under specific conditions

which of course you should then simplify...