SOLUTION: solve 100=-60cos(pi/30(t))+70

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Question 1161394: solve 100=-60cos(pi/30(t))+70
Answer by Edwin McCravy(20065) About Me  (Show Source):
You can put this solution on YOUR website!
+100=-60cos%28expr%28pi%2F30%29t%29%2B70

Subtract 70 from both sides

+30=-60cos%28expr%28pi%2F30%29t%29

+expr%2830%2F%28-60%29%29=cos%28expr%28pi%2F30%29t%29

+expr%28-1%2F2%29=cos%28expr%28pi%2F30%29t%29

The cosine is negative in QII and QIII.



Multiply through by 

           30%2Fpi





Cancel all the πs




matrix%281%2C5%2C%0D%0At%2C%22%22=%22%22%2C20%2B60n%2Cor%2C40%2B60n%29

Those are the two answers

Edwin