Posted by **Greg** on Wednesday, November 14, 2012 at 3:12pm.

What value(s) of theta solve the following equation? cos^2(theta)-cos(theta)-6=0?

I try plugging in different numbers but I am not sure exactly what I am looking for in order to solve?

- Trigonometry -
**Reiny**, Wednesday, November 14, 2012 at 3:50pm
cos^2 Ø - cosØ - 6 = 0

let cosØ = x , then we get

x^2 - x - 6 = 0

(x-3)(x+2) = 0

x = 3 or x = -2

then cosØ = 3 or cosØ = -2

both of these are not possible, since the cosine is defined only between -1 and +1

there is no solution to your equation

- Trigonometry -
**Steve**, Wednesday, November 14, 2012 at 4:43pm
also, you coul dhave reasoned thus:

cos^2θ <= 1

-1 <= cosθ <= 1

no way could you have cos^2θ - cosθ = 6

## Answer This Question

## Related Questions

- Precalculus 2 - Similiarly to a question I asked previously I took the same ...
- Trigonometry - Okay, I have been given a trigonometric equation to solve (sin^2(...
- Calculus - I wanted to confirm that I solved these problems correctly (we had to...
- Trigonometry - Prove the following identities: 1. (tan theta - sin theta)^2 + (1...
- Trigonometry - Prove the following identities: 1. (tan theta - sin theta)^2 + (1...
- Mathamatics - Solve the following trigonometry identities. a) 1-cos2(theta) = ...
- Math - Trigonometry - Let f(x) be a polynomial such that f(cos theta) = cos(4 ...
- Trigonometry - Thank you STEVE!!!!! Suppose that Cos (theta) = 1/square root 2 ...
- science - Sitting on a horizontal track is a mass of 10kg. One end of the track ...
- Trigonometry - Use a sum of difference identity to write the expression as a ...

More Related Questions