6.5 Double Angle Identities
Wednesday, May 01, 2013
3:02 PM
Sin2x = ____________________
Proof: sin2x = 2sinxcosx
cos2x = ______________________
Proof: cos2x = cos2x − sin2x
Other forms of Cos2x
• The 3 versions of cos2x:
Trigonometry (II) Page 1
tan2x =
Examples:
1. Write 10sin3xcos3x as a single trig function
2. Determine the amplitude and period of y = 4sin2xcos2x + 3
3. Solve 3cos2x − 3sin2x + 2 = 0 to 2 dp where 0 ≤ x ≤ 2
different ways.
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Solve 2
Double Angle Proofs: Examples
1. Prove:
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2. Prove:
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5. Show sin3x = 3sinx − 4sin3x
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