Half-Angle Calculator
Compute sin(θ/2), cos(θ/2) or tan(θ/2) using their half-angle identities.
Step-by-step method
- Identify what is given.
- Write the correct half-angle identity.
- Substitute the values and calculate.
Formulas:
Formula: sin(θ/2)
| 1 − cosθ |
| 2 |
Formula: cos(θ/2)
| 1 + cosθ |
| 2 |
Formula: tan(θ/2)
| 1 − cosθ |
| 1 + cosθ |
Example 1: sin(θ/2) with θ = 60°
Step 1 - Identify what is given.
In this problem: The given angle is θ = 60°.
Step 2 - Write the correct half-angle identity.
In this problem: Use the identity: sin(θ/2) = √((1 − cosθ) / 2).
| 1 − cosθ |
| 2 |
Step 3 - Substitute the values and calculate.
In this problem: First find cosθ = cos(60°) = 0.5, then substitute and compute.
| 1 − 0.5 |
| 2 |
Final answer: sin(θ/2) = 0.5
Example 2: tan(θ/2) with θ = 30°
Step 1 - Identify what is given.
In this problem: The given angle is θ = 30°.
Step 2 - Write the correct half-angle identity.
In this problem: Use the identity: tan(θ/2) = √((1 − cosθ) / (1 + cosθ)).
| 1 − cosθ |
| 1 + cosθ |
Step 3 - Substitute the values and calculate.
In this problem: First find cosθ = cos(30°) = 0.8660254, then substitute and compute.
| 1 − 0.8660254 |
| 1 + 0.8660254 |
Final answer: tan(θ/2) = 0.26794919
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