In triangle ABC, when angle A is a right angle, it means that angle A measures exactly 90 degrees. In a right triangle, the side that is opposite to the right angle is known as the hypotenuse. Therefore, in this case, the side that is opposite angle A is the hypotenuse of the triangle.
To clarify further, let’s visualize triangle ABC. If you label the sides opposite angles A, B, and C as a, b, and c respectively, then:
- Side a is opposite to angle A
- Side b is opposite to angle B
- Side c is opposite to angle C
Since angle A is the right angle, the side opposite it, which is side a, is the length of the hypotenuse. This side is typically the longest side in the triangle and is critical in determining the relationships between the other two sides (b and c) through the Pythagorean theorem.
In summary, in triangle ABC with angle A as the right angle, it is side a that is opposite this angle, serving as the hypotenuse of the triangle.