Question

A triangle must have at least two ________.

• A. acute angles
• B. right angles
• C. straight angles
• D. obtuse angles

Answer 1

The correct option is A acute angles

From angle sum property of triangles, sum of the angles should be ${180}^{\circ }$.

Acute angles: As acute angle is less than ${90}^{\circ }$, all the three angles in a triangle can be acute to sum up to ${180}^{\circ }$.

Right angle : Right angle is ${90}^{\circ }$, if two angles in a triangle are right angles then all angles sum upto more than ${180}^{\circ }$.

Straight angle: ${180}^{\circ }$ is a straight angle. A triangle cannot have a straight angle because sum of all the angles in a triangle is ${180}^{\circ }$ and each angle is greater than $0^{\circ }$.

Obtuse angles: Obtuse angle is more than ${90}^{\circ }$, if two are obtuse then sum of all angles exceeds ${180}^{\circ }$.

Hence, a triangle can have two or three acute angle.