How is Cosx = 1/√1+tan²X ?

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Answer 1 · 2018-04-02T14:36:56

Please see below.

We know that,

#(1)1+tan^2x=sec^2x#

#(2)1/secx=cosx#

Here,

#cosx=1/sqrt(1+tan^2x)#

#RHS=1/sqrt(1+tan^2x)...toapply(1)#

#=1/sqrt(sec^2x)#

#=1/secx....toApply(2)#

#=cosx#

#=LHS#