Any1 plz help me in tis problem:

(Bow)if ysinA = xsin(2B + A) then prove that:

(x+y)cot(A+B) = (y-x)cotB

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- June 15th 2008, 11:13 PMSwetabhtransformation formulae in trigo
Any1 plz help me in tis problem:

(Bow)if ysinA = xsin(2B + A) then prove that:

(x+y)cot(A+B) = (y-x)cotB - June 18th 2008, 12:12 AMnikhilhere ir the solution
Hi!swetabh

ysinA=xsin(2B+A)

y/x =sin(2B+A)/sinA

applying componendo and dividendo we get

(y+x)/(y-x)=[sin(2B+A)+sinA]/[sin(2B+A)-sinA].............1

now put sinA =sin(A+B-B) and

sin(2B+A)=sin[B+(B+A)]in the eq1 and expand them as

sin(A+B-B)=sin(A+B)cosB-sinBcos(A+B) and

sin[B+(A+B)]=sinBcos(A+B)+sin(A+B)cosB. By doing this u will finally get

(y+x)/(y-x)=cotB/cot(A+B)

now cross multiply and u will get

(y+x)cot(A+B)=(y-x)cotB