HELP WITH TRIG tan3x (2 Viewers)

littlesmallworld · Oct 14, 2013

Prove for tan 3x= 3tanx-tan^3/1-3tan^2x using sin3x and cos3x

myawesome · Oct 15, 2013

can you take a pic or use brackets or something.. what is tan^3

HeroicPandas · Oct 15, 2013

$$Prove that $ tan3x = \frac{3tanx - tan^3 x}{1-3tan^2x}$

tan^3 = tan³

BagOFyarn · Oct 15, 2013

Drongoski · Oct 15, 2013

If allowed to use formula for tan(A+B):

$tan3x = tan(x+2x) = \frac {tanx + tan2x}{1-tanx \cdot tan2x} = \frac {tan x + \frac {2tan x}{1-tan^2 x}}{1 - tan x \cdot \frac {2tan x}{1-tan^2 x}} \\ \\ = \cdots = \frac {3tan x - tan^3 x}{1 - 3 tan^2 x}$

mahmoudali · Oct 16, 2013

Drongoski said:
If allowed to use formula for tan(A+B):

$tan3x = tan(x+2x) = \frac {tanx + tan2x}{1-tanx \cdot tan2x} = \frac {tan x + \frac {2tan x}{1-tan^2 x}}{1 - tan x \cdot \frac {2tan x}{1-tan^2 x}} \\ \\ = \cdots = \frac {3tan x - tan^3 x}{1 - 3 tan^2 x}$

question says using $\ \ sin(3x)\ \ and\ \ cos(3x)$

Drongoski · Oct 17, 2013

mahmoudali said:
question says using $\ \ sin(3x)\ \ and\ \ cos(3x)$

Oh thanks. Didn't see that.

HELP WITH TRIG tan3x (2 Viewers)

littlesmallworld

Member

myawesome

New Member

HeroicPandas

Heroic!

BagOFyarn

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Drongoski

Well-Known Member

mahmoudali

Member

Drongoski

Well-Known Member

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