How do u prove this ?

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1 Answer
P dilip_k
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#

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