Double Angle Identities

Use a double-angle identity to find the exact value of each expression
cos θ = 4/5 and 270° < θ < 360°
Find sin 2θ

• -1/5

• 24/25

• -24/25

• -25/24

sin2u =

• (sinu)(cosu)

• 2(sinu)(cosu)

• (sinu)^2

• 2(sinu)^2

cos2u =

• 2(sinu)(cosu)

• (cosu)^2 - (sinu)^2

• 2(cosu)^2 - 2

• (sinu)^2 - (cosu)^2

Find the exact value of sin 2x if sin x = 12/13 and x is in the first quadrant. 

• 120/169

• 25/169

• 60/169

• 5/13

Use a double-angle identity to find the exact value of each expression cos θ = 4/5 and 270° < θ < 360° Find sin 2θ

Using the second identity, find Cos(50)

• sin²(25) - cos²(25) 

• cos²(50) - sin²(50)

• cos²(25) - sin²(25)

• sin²(50) - cos²(50) 

Use a double-angle to find the exact value of each expression

cos θ = 4/5 and 270° < θ < 360°Find sin 2θ

• -1/5

• 24/25

• -24/25

• -25/24

Use a double-angle identity to find the exact value of each expression cos θ = 4/5 and 270° < θ < 360° Find sin 2θ

Using the third identity, find Cos(40)

• 2cos² (40) - 1

• 2cos² (20) - 1

• 2cos² (20) + 1

• 2cos² (40) + 1