Math
posted by Simon .
Prove that cos2x=(1tan^2x)/(1+tan^2x)
I can't find any identities that can help me with this. I'm really confused

Math 
drwls
1 + tan^2 x= (cos^2 x+ sin^2 x)/cos^2 x = 1/cos^2 x
Therefore
=(1tan^2x)/(1+tan^2x)= cos^2x  sin^2x
= cos 2x
Respond to this Question
Similar Questions

Math  help really needed
Prove each idenity. 1+1/tan^2x=1/sin^2x 1/cosxcosx=sinxtanx 1/sin^2x+1/cos^2x=1/sin^2xcos^2x 1/1cos^2x+/1+cosx=2/sin^2x and (1cos^2x)(1+1/tan^2x)= 1 I haven't even gotten 'round to sny of the quedtions because the first one is just … 
Math  help really needed
I'm sorry to double post; I don't want to seem impatient, but I really need help with this. Prove each idenity. 1+1/tan^2x=1/sin^2x 1/cosxcosx=sinxtanx 1/sin^2x+1/cos^2x=1/sin^2xcos^2x 1/1cos^2x+/1+cosx=2/sin^2x and (1cos^2x)(1+1/tan^2x)= … 
trig
please help me. use trig. identities to find the exact value. tan 25° + tan 5° / 1 tan 25° tan 5° 
trig
please help me. use trig. identities to find the exact value. tan 25° + tan 5° / 1 tan 25° tan 5° 
Trigonometry
Find the exact value of tan(ab) sin a = 4/5, 3pi/2<a<pi; tan b = sqrt2, pi/2<b<pi identity used is: tan(ab)=(tan atan b)/1+tan a tan b simplify answer using radicals. (a is alpha, b is beta) 
Trigonometry
1.Solve tan^2x + tan x – 1 = 0 for the principal value(s) to two decimal places. 6.Prove that tan y cos^2 y + sin^2y/sin y = cos y + sin y 10.Prove that 1+tanθ/1tanθ = sec^2θ+2tanθ/1tan^2θ 17.Prove that … 
Trig Identities
Proving identities: 1) 1+ 1/tan^2x = 1/sin^2x 2) 2sin^2 x1 = sin^2x  cos^2x 3) 1/cosx  cosx = sin x tan x 4) sin x + tan x =tan x (1+cos x) 5) 1/1sin^2x= 1+tan^2 x How in the world do I prove this...please help... I appreciateyour … 
Trigonometry desperate help, clueless girl here
2. solve cos 2x3sin x cos 2x=0 for the principal values to two decimal places. 3. solve tan^2 + tan x1= 0 for the principal values to two decimal places. 4. Prove that tan^2(x) 1 + cos^2(x) = tan^2(x) sin^2 (x). 5.Prove that tan(x) … 
MathTrigonometry
Show that if A, B, and C are the angles of an acute triangle, then tan A + tan B + tan C = tan A tan B tan C. I tried drawing perpendiculars and stuff but it doesn't seem to work? 
Math
prove sin2x+cos2x+1 tan(pi/4+x) ______________ = __________ sin2x+cos2x1 tanx so what I did tan(x) (1+cos(2x)+sin(2x)=tan(pi/4+x) (1+cos(2x)+sin(2x)