tan(3a) = (3tana - tan3a)/ (1-3tan2a)
so
tan (60) =
3 = (3tan20 - tan
320)/(1-3tan
220)
so
cross multiplying and simplifying
tan
320 - 3
3tan
220 - 3tan20 +
3 = 0
(tan
320 - 3 tan20) = (3
3tan
220 -
3)
squarring on either side
tan620 - 6 tan4 20 + 9tan220 = 27tan420 - 18tan220 + 3
so tan620 - 33tan420 +27tan220 = 3
Moderation Team
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