adv functions
posted by  .
Show that tanx= (sinx/ cosx)
can be written as:
tan(xy) = (tanx  tany) / (1+ tanxtany)

adv functions 
Reiny
write tan (xy)
= sin(xy)/cos(xy)
= [sinxcosy  cosxsiny[/[cosxcosy + sinxsiny]
Now divide everybody by cosxcosy and it will all fall into place.
Respond to this Question
Similar Questions

PreCalc
Trigonometric Identities Prove: (tanx + secx 1)/(tanx  secx + 1)= tanx + secx My work so far: (sinx/cosx + 1/cosx + cosx/cosx)/(sinx/cos x  1/cosx + cosx/cosx)= tanx + cosx (just working on the left side) ((sinx + 1  cosx)/cosx)/((sinx … 
Mathematics  Trigonometric Identities
Prove: sinx + tanx = tanx (1 + cosx) What I have so far: LS: = sinx + tanx = sinx + (sinx / cosx) = (sinx) (cosx) + sinx / cos = tanx (cosx + sinx) I don't know what to do now 
Mathematics  Trigonometric Identities
Prove: (tanx)(sinx) / (tanx) + (sinx) = (tanx)  (sinx) / (tanx)(sinx) What I have so far: L.S. = (sinx / cosx) sinx / (sinx / cosx) + sinx = (sin^2x / cosx) / (sinx + (sinx) (cosx) / cosx) = (sin^2x / cosx) / (cosx / sinx + sinxcosx) 
Trig (inverse functions)
Problem: tan[arccsc(5/3) + arctan(1/4)] My work: let arccsc(5/3)=X and let arctan(1/4)=Y where pi/2<=X<=pi/2, X cannot be 0 and where pi/2<Y<pi/2 so that cscX=5/3 and tanY=1/4 The problem can now be written as tan(X+Y) … 
Trigo
Given that a^2+b^2=2 and that (a/b)= tan(45degee+x), find a and b in terms of sinx and cosx. I don't know what i'm supposed to do, and i don't come to an answer! Help, thanks! my workings: tan(45+x)= (1+tanx)/(1tanx) a/b = (1+tanx)/(1tanx) … 
Trigonometry
Given that a^2+b^2=2 and that (a/b)= tan(45degee+x), find a and b in terms of sinx and cosx. I don't know what i'm supposed to do, and i don't come to an answer! Help, thanks! my workings: tan(45+x)= (1+tanx)/(1tanx) a/b = (1+tanx)/(1tanx) … 
advanced functions
Show that tanx = sinx / cosx can be written as tan(x+y) = (tanx + tany) / (1  tanxtany) 
maths  trigonometry
I've asked about this same question before, and someone gave me the way to finish, which I understand to some extent. I need help figuring out what they did in the second step though. How they got to the third step from the second. … 
Trigonometry Check
Simplify #3: [cosxsin(90x)sinx]/[cosxcos(180x)tanx] = [cosx(sin90cosxcos90sinx)sinx]/[cosx(cos180cosx+sinx180sinx)tanx] = [cosx((1)cosx(0)sinx)sinx]/[cosx((1)cosx+(0)sinx)tanx] = [cosxcosxsinx]/[cosx+cosxtanx] = [cosx(1sinx]/[cosx(1+tanx] … 
Math
Im really struggling with these proving identities problems can somebody please show me how to do these?