Question
(1+tanA tanB)2+(tanA − tanB)2sec2A sec2B= ___
Answer: Option A
:
A
(1+tan A tan B)2+(tan A-tan B)2sec2Asec2B
=1+2tan A tan B+tan2Atan2B+tan2A−2tan A tan B+tan2Bsec2Asec2B
=1+tan2Atan2B+tan2A+tan2Bsec2Asec2B
=1+tan2A+tan2B+tan2Atan2Bsec2Asec2B
=1(1+tan2A)+tan2B(1+tan2A)sec2Asec2B
=(1+tan2A)(1+tan2B)sec2Asec2B
=(sec2A)(sec2B)sec2Asec2B.…(1+tan2θ=sec2θ)
=1
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:
A
(1+tan A tan B)2+(tan A-tan B)2sec2Asec2B
=1+2tan A tan B+tan2Atan2B+tan2A−2tan A tan B+tan2Bsec2Asec2B
=1+tan2Atan2B+tan2A+tan2Bsec2Asec2B
=1+tan2A+tan2B+tan2Atan2Bsec2Asec2B
=1(1+tan2A)+tan2B(1+tan2A)sec2Asec2B
=(1+tan2A)(1+tan2B)sec2Asec2B
=(sec2A)(sec2B)sec2Asec2B.…(1+tan2θ=sec2θ)
=1
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