Prove that (1+tan21) (1+tan28) (1+tan24) (1+tan17) = 4

Answer 1

LS
= (1+tan21) (1+tan28) (1+tan24) (1+tan17)
= [(1+tan21) (1+tan24)] [1+tan28) (1+tan17)]
= [1+ tan24 + tan21 + tan21tan24] [...]
= [1+tan(24+41)(1-tan21tan24) + tan21tan24] [...]
= [1+ tan45(1-tan21tan24) + tan21tan24] [...]
= [1+ 1(1-tan21tan24)) + tan21tan24] [...]
= [ ____ ] [...]

Work out the other set of brackets [...] in a similar fashion.

Answer 2

Good

Answer 3

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