Pre-Calc Double Angle Identities

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cos(2θ)

• cos²θ-sin²θ

• 2sinθcos

• 2cos²+1

• sin²θ-1

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

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

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

Using the second identity, find Cos(50)

• sin²(25) - cos²(25) 

• cos²(50) - sin²(50)

• cos²(25) - sin²(25)

• sin²(50) - cos²(50)