SOLUTION: if sin3theta is equal to cos3theta then prove that theta is equal to 18 degree

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Question 1086238: if sin3theta is equal to cos3theta then prove that theta is equal to 18 degree
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
sin%283%2Atheta%29=cos%283%2Atheta%29
and
sin%5E2%283%2Atheta%29%2Bcos%5E2%283%2Atheta%29=1
cos%5E2%283%2Atheta%29%2Bcos%5E2%283%2Atheta%29=1
2cos%5E2%283%2Atheta%29=1
cos%5E2%283%2Atheta%29=1%2F2
cos%283%2Atheta%29=0+%2B-+sqrt%282%29%2F2
So,
3%2Atheta=45%2B%28360%29k and
3%2Atheta=225%2B%28360%29k
So then,
theta=15%2B120k
theta=75%2B120k
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Theta is 15 not 18 degrees.