1.

( 11 ) \tan 18 ^ { \circ } + \tan 27 ^ { \circ } + \tan 18 ^ { \circ } \cdot \tan 27 ^ { \circ } = 1

Answer»

Let us add 18 and 27 to get 45.

So tan(18+27) = 1 = tan 18 + tan 27/[1 - tan 18.tan 27] or

tan 18 + tan 27 = 1 - tan 18.tan 27, or

tan 18 + tan 27 + tan 18.tan 27 = 1.

Hence the answer is 1.



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