We know from double angle formula that
These identities can also be used to reduce angles
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2x 3x formula - Proving
Last updated at Dec. 4, 2018 by Teachoo
We know from double angle formula that
These identities can also be used to reduce angles
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We know from double angle formula that sin 2x = 2 sin x cos x = 2 tan x / (1 + tan^2 x) cos 2x = cos^2 x - sin^2 x = 1 - 2 sin^2 x = 2 cos^2 x - 1 = 1 - tan^2 x / 1 + tan^2 x tan 2x = 2 tan x / (1 - tan^2 x) These identities can also be used to reduce angles sin x = 2 sin x/2 cos x/2 = 2 tan x/2 / (1 + tan^2 x/2) cos x = cos^2 x/2 - sin^2 x/2 = 1 - 2 sin^2 x/2 = 2 cos^2 x/2 - 1 = 1 - tan^2 x/2 / 1 + tan^2 x/2 tan x = 2 tan x/2 / (1 - tan^2 x/2)