Question

identify the triangle that contains an acute angle for which the sine and cosine ratios are equal.

Explanation:

Step1: Recall trigonometric identity

In a right - triangle, $\sin\theta=\cos(90^{\circ}-\theta)$. When $\theta = 45^{\circ}$, $\sin45^{\circ}=\cos45^{\circ}=\frac{\sqrt{2}}{2}$.

Answer:

The second triangle (with angles $45^{\circ},45^{\circ},90^{\circ}$)