Double Angle Identities A

Front

What is the double angle identity for sin(2θ)?

Back

sin(2θ) = 2(sinθ)(cosθ)

Front

What is the double angle identity for cos(2θ)?

Back

cos(2θ) = cos²θ - sin²θ

Front

If cosθ = 4/5 and 270° < θ < 360°, what is sin(2θ)?

Back

-24/25

Front

What is the value of secx if cosx = -4/5?

Back

-5/4

Front

Using the fourth identity, find Cos(120°).

Back

1 - 2sin²(60°)

Front

What is the double angle identity for tan(2θ)?

Back

tan(2θ) = 2tanθ / (1 - tan²θ)

Front

If sinθ = 3/5, what is cos(2θ)?

Back

cos(2θ) = 2cos²θ - 1 = 2(4/25) - 1 = -17/25

Front

What is the relationship between sin²θ and cos²θ?

Back

sin²θ + cos²θ = 1

Front

If sinu = 1/2, what is sin(2u)?

Back

sin(2u) = 2(sinu)(cosu) = 2(1/2)(√3/2) = √3/2

Front

What is the value of cos(2u) if sinu = 1/2?

Back

cos(2u) = cos²u - sin²u = (√3/2)² - (1/2)² = 3/4 - 1/4 = 1/2