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2016-04-12T12:16:28+05:30

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         \lim_{x \to \ \pi /4}             \frac{1-tanx}{cos2x}
     
          \lim_{x \to \ \pi /4}            \frac{1- \frac{sinx}{cosx} }{cos2x}

         \lim_{x \to \ \pi /4}         \frac{ \frac{cosx-sinx}{cosx} }{cos2x}    
           
         \lim_{x \to \ \pi /4}          \frac{ cosx-sinx }{cosx.cos2x}  

         \lim_{x \to \ \pi /4}            \frac{ cosx-sinx }{cosx(cos^{2}x-sin^{2}x)  } 

         \lim_{x \to \ \pi /4}           \frac{1}{cosx(cosx+sinx)}   

                                  =   \frac{1}{ \frac{1}{ \sqrt{2} }.( \frac{1}{ \sqrt{2} }+\frac{1}{ \sqrt{2} })  }

                                 = \frac{1}{ \frac{1}{ \sqrt{2} }. \frac{2}{ \sqrt{2} }  }
                    
                                 = \frac{1}{ \frac{\sqrt{2} }{ \sqrt{2} } }
            
                                 =  \frac{1}{1}

                                 =1





 


1 5 1
not that , it's below step
there u should write cos x- sinx know.........how it became cos 8x?
It is cosx - sinx
look once
it is not cos 8x