Question

sin x = 3 cos x

Answer 1

There are a couple ways to do this. One way: \[
\sin x=3\cos x \implies \frac{\sin x}{\cos x} =3 \implies \tan x = 3
\]

Answer 2

My favorite, of course:

\(\sin(x) - 3cos(x) = \sqrt{10}\sin(x - atan(3)) = 0\)

Answer 3

Square both sides and add \(\cos^2(x)\) gives you: \[
1=10\cos^2(x)\implies |\cos(x)| = \frac{\sqrt{10}}{10}
\]