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February 6, 2016
Posted by **t54** on Monday, April 4, 2011 at 6:17pm.

tan(165)

- advanced math -
**Reiny**, Monday, April 4, 2011 at 7:31pmI bet it said "find the exact value"

sin(-15) = sin(30-45)

= sin30cos45 - cos30sin45

= (1/2)(√2/2) - (√3/2)(√2/2) = (√2 - √6)/4

tan(165) = tan(120+45)

= (tan120 + tan45)/(1-tan120tan45)

tan 120 = -tan60 = -√3

so back into the above result

= (-√3 + 1)/(1 - (-√3)(1)) = (1-√3)/(1+√3)