91Ó°ÊÓ

Use an Addition or Subtraction Formula to write the expression as a trigonometric function of one number, and then find its exact value. $$\frac{\tan 73^{\circ}-\tan 13^{\circ}}{1+\tan 73^{\circ} \tan 13^{\circ}}$$

Solving Trigonometric Equations Solve the equations by factoring. \(3 \tan ^{3} \theta-3 \tan ^{2} \theta-\tan \theta+1=0\)

Verify the identity. $$\frac{\cos u \sec u}{\tan u}=\cot u$$

Use the Addition Formula for sine to prove the Double-Angle Formula for sine.

Write the product as a sum. $$\cos 5 x \cos 3 x$$

Prove the identity. $$\cot 2 x=\frac{1-\tan ^{2} x}{2 \tan x}$$

Use a Sum-to-Product Formula to show the following. $$\cos 100^{\circ}-\cos 200^{\circ}=\sin 50^{\circ}$$

These identities involve trigonometric functions as well as other functions that we have studied. $$\ln |\tan x \sin x|=2 \ln |\sin x|+\ln |\sec x|$$