# Solving Trigonometric Equation

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• April 20th 2009, 01:28 PM
jepal
Solving Trigonometric Equation
Find exact solotions.

2cosx+3tanx=0
2cosx+3sinx/cosx=0 *cosx
2cos^2x+sinx=0 ***Im stuck here any hints, I tried to use the double angel formula but its cos 2x not 2cosx! any hints!
• April 20th 2009, 01:39 PM
skeeter
Quote:

Originally Posted by jepal
Find exact solotions.

2cosx+3tanx=0
2cosx+3sinx/cosx=0 *cosx
2cos^2x+sinx=0 ***Im stuck here any hints, I tried to use the double angel formula but its cos 2x not 2cosx! any hints!

$\frac{2\cos^2{x}}{\cos{x}} + \frac{3\sin{x}}{\cos{x}} = 0$

$2\cos^2{x} + 3\sin{x} = 0$

$2(1 - \sin^2{x}) + 3\sin{x} = 0$

solve the quadratic for $\sin{x}$