Posted by **Josh** on Tuesday, July 19, 2011 at 1:24am.

find the exact value of sin 11pi/12 using the sum or difference formula.

- Calculus -
**Damon**, Tuesday, July 19, 2011 at 5:42am
11/12 = 2/12 + 9/12 = 1/6 + 3/4

sin pi/6 = 1/2

cos pi/6 = (1/2) sqrt 3

sin 3 pi/4 = (1/2)sqrt 2

cos 3 pi/4 = -(1/2) sqrt 2

- Calculus -
**Reiny**, Tuesday, July 19, 2011 at 8:12am
Some students feel more comfortable working with degrees.

sin(11π/12) = sin 165° = sin 15° by the CAST rule

sin15° = sin(45°-30°)

= sin45°cos30° - cos45°sin30°

= (√2/2)(√3/2) - (√2/2)(1/2)

= (√6 - √2)/4

sin 11π/12 = (√6-√2)/4

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