SOLUTION: How to solve it: 4 sin 5Pi/12 cos 5pi/12 = ? Answers: a ) √ 2 b) 1 c) √ 3 d) - 1

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Question 824157: How to solve it:
4 sin 5Pi/12 cos 5pi/12 = ?
Answers:
a ) √ 2
b) 1
c) √ 3
d) - 1
Answer by lwsshak3(11628) About Me  (Show Source):
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How to solve it:
4 sin 5Pi/12 cos 5pi/12 = ?
Answers:
a ) √ 2
b) 1
c) √ 3
d) - 1
***
Identities:(half-angle formulas for sin and cos)
=√(2+√3)/2
..
=√(2-√3)/2
..
4 sin 5Pi/12 cos 5pi/12 = 4*√(2+√3)/2*√(2-√3)/2=4*√(4-3)/4=4*1/4=1
ans: b) 1