Posted by edward on .
in triangle abc if acosA= bcosB then how to prove the triangle is isosceles or right angled

mathematics 
Steve,
we know that a/sinA = b/sinB
if acosA = bcosB, then
a/cosB = b/cosA
b = acosA/cosB
b = asinB/sinA
so, acosA/cosB = asinB/sinA
cosAsinA = sinBcosB
sin2A = sin2B
means A=B and the triangle is isoceles