# Trig - Help with tan(arccos(x/3))

TKDKicker89
Can anyone help asap?

tan(arccos x/3)

THanks

Gold Member
MHB
Draw a right triangle. If arccos x/3 = theta, draw that triangle.

if $$\theta=cos^{-1} \frac{x}{3}$$
then $$\frac{x}{3}$$ is the cosine of $$\theta$$
You can use the pythagorean theorem to find the sine of $$\theta$$
$$\cos^2 \theta + \sin^2 \theta = 1$$
The tangent of $$\theta$$ is $$\frac{sin \theta}{cos \theta}$$