Question

1. which of the following is not a right - triangle?

a. a triangle with angles 45°, 45°, and 90°
b. a triangle with angles 20°, 70°, and 90°
c. a triangle with angles 30°, 60°, and 90°
d. a triangle with angles 60°, 60°, and 60°

Explanation:

Step1: Recall right - triangle definition

A right - triangle has one angle equal to 90°.

Step2: Analyze option a

It has a 90° angle, so it's a right - triangle.

Step3: Analyze option b

It has a 90° angle, so it's a right - triangle.

Step4: Analyze option c

It has a 90° angle, so it's a right - triangle.

Step5: Analyze option d

All angles are 60°, no 90° angle.

Answer:

d. A triangle with angles 60°, 60°, and 60°