SOLUTION: Find the exact value of: sin 70degrees cos 40degrees - cos 70degrees sin 40degrees.

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Question 149423: Find the exact value of:
sin 70degrees cos 40degrees - cos 70degrees sin 40degrees.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
sin%2870%29%2Acos%2840%29+-+cos%2870%29%2Asin%2840%29 Start with the given expression.


sin%2870-40%29 Rewrite the expression using the identity sin%28x%29%2Acos%28y%29+-+cos%28x%29%2Asin%28y%29=sin%28x-y%29


sin%2830%29 Subtract


1%2F2 Take the sine of 30 to get 1/2


So sin%2870%29%2Acos%2840%29+-+cos%2870%29%2Asin%2840%29=1%2F2