SOLUTION: Prove that {{{(sin(a+b))/(tana+tanb)=cosacosb }}} using only the left side.

Algebra ->  Trigonometry-basics -> SOLUTION: Prove that {{{(sin(a+b))/(tana+tanb)=cosacosb }}} using only the left side.      Log On


   

Question 1074123: Prove that %28sin%28a%2Bb%29%29%2F%28tana%2Btanb%29=cosacosb+ using only the left side.
Answer by josgarithmetic(39623) About Me  (Show Source):
You can put this solution on YOUR website!






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If you look at the fraction on the left carefully, you will easily make the steps to show that it is equal to 1.
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1%2Acos%28a%29cos%28b%29




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Used angle sum identity sin%28a%2Bb%29=sin%28a%29cos%28b%29%2Bcos%28a%29sin%28b%29