SOLUTION: Use a sum or difference formula to find the exact value of the following.
cos 7pi/10 * cos 2pi/15 + sin 7pi/10 * sin 2pi/15= ???
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-> SOLUTION: Use a sum or difference formula to find the exact value of the following.
cos 7pi/10 * cos 2pi/15 + sin 7pi/10 * sin 2pi/15= ???
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Question 890708: Use a sum or difference formula to find the exact value of the following.
cos 7pi/10 * cos 2pi/15 + sin 7pi/10 * sin 2pi/15= ??? Answer by lwsshak3(11628) (Show Source):
You can put this solution on YOUR website! Use a sum or difference formula to find the exact value of the following.
cos 7pi/10 * cos 2pi/15 + sin 7pi/10 * sin 2pi/15= ???
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Identity: cos(x-y)=cosxcosy+sinxsiny
cos 7pi/10 * cos 2pi/15 + sin 7pi/10 * sin 2pi/15
=cos(7π/10-2π/15)=cos(21π/30-4π/30)=cos(17π/30)
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