Solve this Trigonometry equation
Favorites|Homepage
Subscriptions | sitemap
HOME > > Solve this Trigonometry equation

Solve this Trigonometry equation

[From: ] [author: ] [Date: 12-02-29] [Hit: ]
......
Solve 4cos2A = 3cosA for 90º≤A≤180º.

-
4 cos(2a) = 3 cos(a)

4 cos^2(a) - 4 sin^2(a) = 3 cos(a)

8 cos^2(a) - 3 cos(a) - 4 = 0

This is now a quadratic equation in cos(a), hence

cos(a) = (1/16)( 3 +/- sqrt(137) ) = -0.544044 and 0.919044

The solution in the designated interval is

a = arccos( -0.544044 ) = 122.959 degrees
1
keywords: equation,Trigonometry,this,Solve,Solve this Trigonometry equation
New
Hot
© 2008-2010 http://www.science-mathematics.com . Program by zplan cms. Theme by wukong .