Question

[
begin{array}{l}a cos A=b cos ^{N} frac{a}{b}=frac{sin A}{sin B}=frac{cos A}{cos B} # sin (A-B)=sin A cos B-C O A A sin B=0end{array}
]
( A=B ) and ( 50 quad A+B+C=2 A+C=pi )
( therefore ) The ( triangle ) is inceles

# (i) If the cosines of two angles of a triangle are proportional to the opposite sides, show that the triangle is isosceles.

Solution