Question

Help with a trig problem please?

Answer 1

[\[\cos^2\theta + 2\sin \theta \cos \theta-\sin^2\theta=0\] is the original \[\cos(2\theta) + \sin (2\theta) = 0\] then I use formulas \to get \to this\]

Answer 2

looks good, divide \(\cos(2\theta)\) through out assuming it is not 0

Answer 3

\[\cos(2\theta) + \sin (2\theta) = 0\]
\[1 + \frac{\sin (2\theta)}{\cos(2\theta)} = 0\]
\[\tan(2\theta) = -1\]

see if you can take it home from here