If $\cos ^2 A+\cos ^2 C=\sin ^2 B$, then $\triangle A B C$ is

Given, $\cos ^2 A+\cos ^2 C=\sin ^2 B$ Obviously it is not an equilateral triangle because $A=B=C=60^{\circ}$ does not satisfy the given condition. But $B=90^{\circ}$, then $\sin ^2 B=1$ and $\begin{aligned} \cos ^2 A+\cos ^2 C= & \cos ^2 A+\cos ^2\left(\frac{\pi}{2}-A\right) \\ = & \cos ^2 A+\sin ^2 A=1 \end{aligned}$
Hence, this satisfies the condition, so it is a right angled triangle but not necessarily isosceles triangle.