Q : if $\displaystyle Cos B / a = Cos A / b$
Prove that : $\displaystyle a=b$ and $\displaystyle c^2$$\displaystyle =$$\displaystyle a^2$$\displaystyle +$$\displaystyle b^2$
Q : if $\displaystyle Cos B / a = Cos A / b$
Prove that : $\displaystyle a=b$ and $\displaystyle c^2$$\displaystyle =$$\displaystyle a^2$$\displaystyle +$$\displaystyle b^2$
What have you tried? You could start by using the cosine rule to express cos A and cos B in terms of a, b and c. Then try to simplify the resulting equation.
Edit. After checking the question, I think that you have stated it wrongly. It should say
Prove that : $\displaystyle a=b$ or $\displaystyle c^2=a^2+b^2$.
yes it is or not and i made alot of tries but all reach to same result :
$\displaystyle b^2$$\displaystyle ($$\displaystyle c^2$$\displaystyle -$$\displaystyle b^2$$\displaystyle ) =$$\displaystyle a^2$$\displaystyle ($$\displaystyle c^2$$\displaystyle -$$\displaystyle a^2$$\displaystyle )$