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Differentiate Sin sqrt x from first principles
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http://math.stackexchange.com/questions/1629163/how-to-find-derivative-of-sin-sqrtx-using-difference-quotient
Differentiate Sin sqrt x from first principles
http://math.stackexchange.com/questions/1629163/how-to-find-derivative-of-sin-sqrtx-using-difference-quotient