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Trig Identity: Can you prove that tan(x) = sin(2x)/[1+cos(2x)]. Thanks?
6 Answers
- gilviLv 71 decade agoFavorite Answer
tan(x) = sin(2x)/[1+cos(2x)]
sin(2x) = 2sinxcosx;
cos(2x) = cos^2(x) -sin^2(x)
tan(x) = 2sinxcosx/[1+cos^2(x) -sin^2(x)]
tan(x) = 2sinxcosx/[1+cos^2(x) -1 +cos^2(x)] <= sin^2(x) = 1 - cos^2(x)
tan(x) = 2sinxcosx/[2cos^2(x)]
tan(x) = sinx/[cos(x)]
tan(x) = tan(x);
- Anonymous5 years ago
RHS = (tan pi/4 - tan x)/(a million+ tan x tan pi/4) = (a million-tan x)/(a million+an x) = (cos x -sin x)/(sin x+ cos x) = ( cos x- sin x)(sin x + cos x)/(sin x+ cos x)^2 = (cos ^2 x -sin ^2 x)/(sin ^2 x+ cos^2 x + 2 sin x cos x) = cos 2x/(a million+ sin 2x)
- ?Lv 41 decade ago
tan (x) = sin (2x)/[1+cos (2x)]
forms of equation that may derived:
sin (2x) = 2sin x cos x
cos (2x) = 2cos² x - 1
tan x = [2sin x cos x] / [1+2cos² x -1]
tan x = [2sin x cos x] / [1-1+2cos² x]
tan x = [2sin x cos x] / [2cos² x] ..... cancel the 2 of
numerator and denominator gives you...
tan x = [sin x cos x] / [cos² x] ......... divide the numerator and denominator.
tan x = sin x/cos x
tan x = tan x
- cidyahLv 71 decade ago
sin(2x)/[1+cos(2x)= 2 sin(x) cos(x) / 1+1-2sin^2(x)
using sin(2x)=2 sin(x) cos(x)
and cos(2x)=1-2sin^2(x)
=2 sin(x) cos(x) / 2-2sin^2(x)
=2 sin(x) cos(x) / 2(1-sin^2(x))
=2 sin(x) cos(x) / 2 cos^2(x) = sin(x)/cos(x)
=tan(x)