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Questions and Answers
What is the formula for sin(2θ) in terms of θ?
What is the formula for sin(2θ) in terms of θ?
What is the formula for cos(2θ) in terms of θ?
What is the formula for cos(2θ) in terms of θ?
What is the formula for tan(θ/2) in terms of θ?
What is the formula for tan(θ/2) in terms of θ?
What is the formula for sin(θ/2) in terms of θ?
What is the formula for sin(θ/2) in terms of θ?
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What is the formula for cos(θ/2) in terms of θ?
What is the formula for cos(θ/2) in terms of θ?
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Study Notes
Trigonometric Identities
Double Angle Formulas
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Sine Double Angle Formula:
- sin(2θ) = 2sin(θ)cos(θ)
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Cosine Double Angle Formulas:
- cos(2θ) = cos²(θ) - sin²(θ) = 1 - 2sin²(θ) = 2cos²(θ) - 1
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Tangent Double Angle Formula:
- tan(2θ) = 2tan(θ) / (1 - tan²(θ))
Half Angle Formulas
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Sine Half Angle Formula:
- sin(θ/2) = ±√((1 - cos(θ))/2)
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Cosine Half Angle Formula:
- cos(θ/2) = ±√((1 + cos(θ))/2)
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Tangent Half Angle Formula:
- tan(θ/2) = ±√((1 - cos(θ))/(1 + cos(θ)))
- tan(θ/2) = sin(θ) / (1 + cos(θ))
- tan(θ/2) = (1 - cos(θ)) / sin(θ)
Trigonometric Identities
Double Angle Formulas
- Double angle formulas are used to find the sine, cosine, and tangent of twice an angle.
- Sine Double Angle Formula: sin(2θ) = 2sin(θ)cos(θ)
-
Cosine Double Angle Formulas: cos(2θ) has three forms:
- cos²(θ) - sin²(θ)
- 1 - 2sin²(θ)
- 2cos²(θ) - 1
- Tangent Double Angle Formula: tan(2θ) = 2tan(θ) / (1 - tan²(θ))
Half Angle Formulas
- Half angle formulas are used to find the sine, cosine, and tangent of half an angle.
- Sine Half Angle Formula: sin(θ/2) = ±√((1 - cos(θ))/2)
- Cosine Half Angle Formula: cos(θ/2) = ±√((1 + cos(θ))/2)
-
Tangent Half Angle Formula: tan(θ/2) has three forms:
- ±√((1 - cos(θ))/(1 + cos(θ)))
- sin(θ) / (1 + cos(θ))
- (1 - cos(θ)) / sin(θ)
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Description
Test your knowledge of trigonometric identities, including double angle formulas and half angle formulas for sine, cosine, and tangent.