How Do I Solve the Equation 117.72 = 100sin2x + 28cosx for x?

[Todd0012]

Stuck please help -- 117.72=100sin2x + 28cosx

Im trying to find an angle and I am stuck

117.72=100sin2x + 28cosx

What do i do now?

 

[SteamKing]

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.

 

[neemer]

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

 

[Todd0012]

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

Thats a trig Identity?

 

[neemer]

ah my memory was bad that one is for cos2x sorry