Question

if tanA =K cotB then cos(A-B) /cos(A+B)
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Answer 1

Answer:

1+k/1-k

Step-by-step explanation:

tanA=k cotB

tanA=k 1/tanB

tanA tanB=k ------(1)

now,

cos(A-B)/cos(A+B)=cosAcosB+sinAsinB/ cosAcosB-sinAsinB

cos(A-B)/cos(A+B)=1+tanA tanB/1-tanA tanB {dividing num. and denom. by cosAcosB}

cos(A-B)/cos(A+B)=1+k/1-k { using equation (1)}