I'm stuck on these questions:
1. Find theta in the interval 0 <theta<360 that satisfies the equation $\displaystyle cos^2theta=sin^2theta+1$
2. $\displaystyle 2cos^2x+2cosx-1=0$
Hello,
recall the identity cos²x+sin²x=1.
hence your equation becomes :
$\displaystyle 1-\sin^2 \theta=\sin^2 \theta+1$
which simplifies to :
$\displaystyle 2 \sin^2 \theta=0$
$\displaystyle \sin \theta=0$
Let $\displaystyle X=\cos(x)$2. $\displaystyle 2cos^2x+2cosx-1=0$
Solve the quadratic
and then find the solutions ^^