Monday

March 30, 2015

March 30, 2015

Posted by **help me out it's urgent** on Saturday, October 6, 2012 at 12:20pm.

- trignometry -
**Reiny**, Saturday, October 6, 2012 at 12:45pmcos 2x

= cos(x+x)

= cosxcosx - sinxsinx

= cos^2 x - sin^2 x

= cos^2 x - (1 - cos^2 x)

= 2 cos^2 x - 1, the last part of your equation.

all we need it to look at now is the middle part of

(1 - tan^2 x)/(1 + tan^2 x) , notice the necessary brackets

= (1 - sin^2 x/cos^2 x)/(1 + sin^2 x/cos^2 x)

= [ (cos^2 x - sin^2 x)/cos^2 x ]/[ (cos^2 x + sin^2 x)/cos^2 x ]

= (cos^2 x - sin^2 x)/cos^2 x * cos^2 x/(cos^2 x + sin^2 x)

= (cos^2 x - sin^2 x)/1

= cos^2 x - sin^2 x

as seen above

**Answer this Question**

**Related Questions**

Math-Trigonometry - Show that if A, B, and C are the angles of an acute triangle...

Trig....... - I need to prove that the following is true. Thanks (2tanx /1-tan^x...

math - if sin(x+α)=2cos(x-b) show tan x such that : tan x=(2-tan&#...

Trigonometry - Find the exact value of tan(a-b) sin a = 4/5, -3pi/2<a<-pi...

Trig. - sec^2xcotx-cotx=tanx (1/cos)^2 times (1/tan)-(1/tan)=tan (1/cos^2) times...

verifying identities - how do you veriy tan x + Cot y -------------- = tan y + ...

maths-trignometry - Prove that tan-1 (1/7) + tan-1 (1/13) = tan-1(2/9)

trignometry - Tan4x=4tanx(1-tan^x)/1-6tan^x+tan^^x ,prove

trignometry - 1. if sin 2A = Psin2B, prove that tan(A+B)/tan(A-B)=P+1/P-1.

Math - Prove that cos2x=(1-tan^2x)/(1+tan^2x) I can't find any identities that ...