In the image, triangle ABC is a right triangle with a right angle at $B$. In any right triangle, the hypotenuse is the side opposite the right angle, and it is the longest side of the triangle.

In this case, the hypotenuse is side $AC$, as it is opposite the right angle at $B$.

Would you like to explore more about right triangles or ask any other related questions?

Here are five questions to expand your understanding:

1. How can we calculate the length of the hypotenuse using the Pythagorean theorem?
2. What are the relationships between the angles in a right triangle?
3. How can we find the area of a right triangle?
4. What is the importance of trigonometric ratios in a right triangle?
5. How can we apply the concept of similar triangles in right triangles?

Tip: In a right triangle, the Pythagorean theorem states that $a^2 + b^2 = c^2$, where $c$ is the hypotenuse.