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рдкреНрд░рд╢реНрди
`(tan A + tanB )/(cot A + cot B) = tan A tan B`
рдЙрддреНрддрд░
LHS = `(tan A + tanB )/(cot A + cot B) `
=`(tan A + tan B)/(1/ tan A + 1/ tanB)`
=` (tan A + tan B)/( (tan A+tan B)/ (tan A tan B)`
=`(tan A tan B ( tan A + tan B))/((tan A + tan B ))`
= ЁЭСбЁЭСОЁЭСЫЁЭР┤ ЁЭСбЁЭСОЁЭСЫЁЭР╡
= RHS
Hence, LHS = RHS
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