Trigonometric Double Angle Identities Quiz

Which expression is equivalent to 1/1-2sin^2(x)?

1/cos(2x)

What is the error in this derivation?

In step 3, cos^2(x) - 1 - cos^2(x) should be cos^2(x) - 1 + cos^2(x).

Simplify cos(2x)/cos(x)+sin(x)

cos(x)+sin(x)

Which expression is equal to 2sin(pi/10)cos(pi/10)?

sin pi/5

Suppose cos(x)=-1/3 where pi/2<x<pi. What is the value of tan(2x)?

2 sqrt8/7

Which expression is equivalent to cos(4x)?

2(2cos^2(x) - 1)^2 - 1

Which derivation correctly uses the cosine sum identity to prove the cosine double angle identity?

First Table A

Consider the derivation of sin(2x). Where is the error?

Step 3 should read = 2sin(x)cos(x).

Let sin(2x) - sin(x) = 0, where 0 ≤ x < 2π. What are the possible solutions for x?

{0,pi/3,pi,5pi/3}

Let cos(2x) - cos(x) = 0, where 0° ≤ x ≤ 180°. What are the possible values for x?

0° or 120°