Friday

August 1, 2014

August 1, 2014

Posted by **Katlynn** on Wednesday, March 6, 2013 at 9:55pm.

cos(x)(9cos(x) + 4) = 4; [0, 2π)

- Trigonometry -
**Reiny**, Thursday, March 7, 2013 at 8:55amexpand first

9cos^2 x + 4cosx - 4 = 0

let y = cosx

9y^2 + 4y - 4 = 0

y = (-4 ±√160)/18 , using the formula

= (-4 + 4√10)/18

= (-2 ± 2√10)/9

= appr .480506 or appr -.92495

then cosx = .480506 or cosx = -.92495

x = 61.28° or 298.72° or 157.66° or 202.34°

**Related Questions**

Trigonometry - Use inverse trigonometric functions to find the solutions of the ...

Trigonometry - Use inverse trigonometric functions to find the solutions of the ...

Trigonometry - Use inverse trigonometric functions to find the solutions of the ...

Trigonometry - Find all solutions between 0 and 2pi. Round to two decimal places...

Math: Calculus - Can someone help me out here with these two problem? I have ...

algebra help - I need help with this problem not understanding it. Give exact ...

Math - Give the exact and approximate solutions to three decimal places. X^2-7x+...

precalculus - Find all solutions of the given equation. (Enter your answers as a...

precal - Find all solutions of the given equation. (Enter your answers as a ...

Calculus - The equation 10(x-1)(x-2)(x-3) = 1 has three real solutions a<b<...