Question

A triangle whose all angles are less than ${90}^{\circ }$ is called a/an ________ triangle.

• A. acute
• B. obtuse
• C. right
• D. right isosceles

Answer 1

The correct option is A acute

A triangle whose all angles are less than ${90}^{\circ }$ or acute, is called an acute angled triangle.

However, the phrase “at least one acute angle” means one or more than one acute angle.

Now, a triangle can have one obtuse angle and two acute angles.

For e.g. ${120}^{\circ },{30}^{\circ }$ and ${30}^{\circ }$.

In that case, the triangle is called an obtuse angled triangle, not acute angled triangle.