How do u prove this ?

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1 Answer
Apr 17, 2018

LHS=(cos^2(alpha+beta)+cos^2(alpha -beta))/(2sin^2alphasin^2beta)

=((cosalphacosbeta-sinalphasinbeta)^2+(cosalpha cosbeta+sinalphasinbeta)^2)/(2sin^2alphasin^2beta)

=(2(cos^2alphacos^2beta+sin^2alphasin^2beta))/(2sin^2alphasin^2beta)

=(cos^2alphacos^2beta)/(sin^2alphasin^2beta)+(sin^2alphasin^2beta)/(sin^2alphasin^2beta)

=cot^2alphacot^2beta+1=RHS