Posted by **Lucy X** on Sunday, December 7, 2008 at 10:39pm.

Can you please help me solve this trig equation for 0 ≤ x ≤ 2π?

9sin^2(x)-6cos(x)-10=0

Thank you!

- Trigonometry -
**drwls**, Sunday, December 7, 2008 at 10:47pm
Turn it into a quadratic equation for u = cos x.

9(1 - cos^2x)-6 cos x - 10 = 0

-9u^2 -6u -1 = 0

(3u +1)^2 = 0

cos x = -1/3

There will be solutions in the second and third quadrant

- Trigonometry -
**Lucy X**, Sunday, December 7, 2008 at 10:52pm
Thanks.

Am I supposed to use the inverse trig function to find the angle?

## Answer This Question

## Related Questions

- Differentials (calc) - Solve the Poisson equation ∇^2u = sin(πx) for ...
- PRE - CALCULUS - Eliminate the parameter t. Find a rectangular equation for the ...
- Advanced Functions/Precalculus - Trigonometry Questions 1. Solve the equation ...
- Advanced Functions/Precalculus - Trigonometry Questions 1.) Find the exaqct ...
- algebra 1 help please - 4) a student score is 83 and 91 on her first two quizzes...
- calculus - In spherical coordinates, the inequalities 0≤ρ≤2, 3...
- pre-calculus - y=tanx -2π≤x≤2π y=cotx -2π≤x&#...
- Pre Calculus - sec x = -2 , π ≤ x ≤ 3π Use a calculator to...
- Algebra 2 - Solve. 4a-2≤a+1≤3a+4 4a-2-1≤a+1-1≤3a+4-1 4a-...
- PreCalc - I'm not sure how to solve these with calculator. sec x = -2 , π...

More Related Questions