Answers

2014-05-18T12:04:34+08:00
Cot (x) cos (x) = csc (x) - sin (x) 
=  \frac{cos(x)}{sin(x)} cos (x) =  \frac{1}{sin(x)} - sin (x) 
 \frac{ cos^{2}(x) }{sin(x)}  \frac{1}{sin(x)} -  \frac{ sin^{2}(x) }{sin(x)}
 \frac{ cos^{2}(x) }{sin(x)} =  \frac{1- sin^{2}(x) }{sin(x)}
removing the denominator in both sides
= cos^{2} (x) = 1- sin^{2} (x)
= cos^{2} +  sin^{2} = 1
this equation is actually the identity. 
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