Which description characterizes a right triangle?

Which description characterizes a right triangle?

• A. A triangle with all angles less than 90 degrees.
• B. A triangle with exactly one 90 degree angle.
• C. A triangle with three equal sides.
• D. A triangle with two equal angles.

Answer: (B)

Right triangles are triangles that contain a 90-degree angle. The description with exactly one 90-degree angle matches this idea, since a single right angle defines the triangle as right. Remember the sum of interior angles is 180 degrees, so you can't have more than one right angle in a triangle, and having one right angle is the defining feature. If every angle is less than 90, the triangle is acute, not right. If all three sides were equal, the figure would be equilateral, which has 60-degree angles and no right angle. If two angles are equal, the figure is isosceles; that condition describes symmetry of angles, not specifically a 90-degree angle, so it doesn't identify a right triangle.

Right triangles are triangles that contain a 90-degree angle. The description with exactly one 90-degree angle matches this idea, since a single right angle defines the triangle as right. Remember the sum of interior angles is 180 degrees, so you can't have more than one right angle in a triangle, and having one right angle is the defining feature. If every angle is less than 90, the triangle is acute, not right. If all three sides were equal, the figure would be equilateral, which has 60-degree angles and no right angle. If two angles are equal, the figure is isosceles; that condition describes symmetry of angles, not specifically a 90-degree angle, so it doesn't identify a right triangle.