1. Mar 26, 2014

Todd0012

Im trying to find an angle and im stuck

117.72=100sin2x + 28cosx

What do i do now?

2. Mar 27, 2014

SteamKing

Staff Emeritus
You can always assume a value of x and evaluate the RHS of the equation to see if it equals the LHS.

You can graph the RHS of the equation for different values of x, and then draw a line y= 117.72 and use the intersection points to estimate the values of x which are the solutions.

You can use trig identities on the RHS to see if you obtain an equivalent expression in x which may be more amenable to solution.

Take yer pick.

3. Mar 27, 2014

neemer

use the identity (2cos(x)^2 -1) = sin2x to make it a quadratic equation with cosx instead of x

4. Mar 27, 2014

Todd0012

(2cos(x)^2 -1) = sin2x

Thats a trig Identity?

5. Mar 27, 2014

neemer

ah my memory was bad that one is for cos2x sorry