Posted by **shandra** on Monday, January 2, 2012 at 10:04pm.

Given tan theta=-8/5 and sin theta < 0, find cos theta.

- Math-pre-calculus -
**Reiny**, Monday, January 2, 2012 at 10:40pm
if tanŲ < 0 and sinŲ < 0 , then Ų must be in quad IV

from tanŲ = -8/5 in IV, we have x = 5, y = -8

r^2 = 25+64 = 89

r = √89

then cosŲ = 5/√89

## Answer this Question

## Related Questions

- Calculus - I wanted to confirm that I solved these problems correctly (we had to...
- math - I have a question I have been working on since yesterday and I am not ...
- Math-pre-calculus - Given tan theta=-8/5 and sin theta < 0, find cos theta.
- Maths- complex numbers - Find tan(3 theta) in terms of tan theta Use the formula...
- Algebra II - Multiple Choice Which expression is NOT equivalent to 1? (theta) ...
- Precalculus check answers help! - 1.) Find an expression equivalent to sec theta...
- Precalculus check answers help! - 1.) Find an expression equivalent to sec theta...
- trigonometry - can you correct the rest for me please? Express each as a ...
- trigonometry - can you correct the rest for me please? Express each as a ...
- trigonomtry - can you correct the rest for me please? Express each as a function...

More Related Questions