Question 1187016
1. Apply a formula to find the exact value of the expression. Make sure to 
write down the formula first. Do not use a calculator. Simplify your answer 
completely. 

  sin15° 
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sin(15) = sin(30/2)sqrt
From "Half angle formulas" on Wikipedia:
{{{sin^2(30/2) = (1-cos(30))/2}}}
See Wikipedia Trigonometric functions to check your answer.
It's quite tedious and easy to make an error.
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cos(11𝜋/12) = cos(165)
= cos(120 + 45)
= cos(120)*cos(45) - sin(120)*sin(45)
= {{{-0.5*sqrt(2)/2 - (sqrt(3)/2)*sqrt(2/2)}}}
= {{{-sqrt(2)/4 - sqrt(6)/4}}}
= {{{-(sqrt(2) + sqrt(6))/4}}}