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Trigonometry Simplifying trig expression

daigo

Member
Jun 27, 2012
60
I have to simplify (or get it in terms of tan I guess?) [tex]\cot (\frac{2\pi }{3} - x)[/tex]



I'm not sure how to get the reference angle and subtract the angle 'x' from it to get an expressional value...how would I do this?
 

soroban

Well-known member
Feb 2, 2012
409
Hello, daigo!

[tex]\text{Simplify: }\:\cot(\tfrac{2\pi}{3} - x)[/tex]

[tex]\text{Identity: }\:\tan(A - B) \;=\;\frac{\tan A - \tan B}{1 + \tan A\tan B}[/tex]

[tex]\cot(\tfrac{2\pi}{3} - x) \;=\;\frac{1}{\tan(\frac{2\pi}{3} - x)} \;=\;\frac{1 + \tan\frac{2\pi}{3}\tan x}{\tan\frac{2\pi}{3} - \tan x} [/tex]

. . . . . . . . .[tex]=\; \frac{1 + (\text{-}\sqrt{3})\tan x}{(\text{-}\sqrt{3}) - \tan x} \;=\; \frac{1 - \sqrt{3}\tan x}{\text{-}\sqrt{3} - \tan x}[/tex]

. . . . . . . . .[tex]=\; \frac{\sqrt{3}\tan x - 1}{\tan x + \sqrt{3}}[/tex]