Prove that tan6.tan42.tan66.tan78=1

Steps to prove tan6.tan42.tan66.tan78=1

L.H.S

=tan6.tan42.tan66.tan78

=tan6.tan(60-6).tan(60+6).tan42.tan78/tan54

=tan3(6).tan42.tan78/tan54

=tan18.tan42.tan78/tan54

=tan18.tan(60-18).tan(60+18)/tan54

=tan3(18)/tan54

=tan54/tan54

=1

=R.H.S

Hence tan6.tan42.tan66.tan78=1 is proved.

Detail Information:-

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