Acute and Obtuse Angles

Angles are the shapes made when two lines meet. Some angles are small and sharp, while others are wide and open. Acute angles are smaller than a right angle. Obtuse angles are bigger than a right angle. Learning about angles helps us understand shapes.

Acute Angles

An acute angle is less than 90 degrees. It looks sharp and pointy, like the tip of a pencil. The hands of a clock make an acute angle at 1:00. Many triangles have acute angles. The word 'acute' actually means 'sharp' in Latin.

Obtuse Angles

An obtuse angle is more than 90 degrees but less than 180 degrees. It looks open and wide. You can see obtuse angles in reclining chairs and open books. The word 'obtuse' means 'blunt' or 'not sharp.' Some triangles have one obtuse angle, and those are called obtuse triangles.

Fun Facts

• An angle of exactly 180 degrees is a straight line.
• A full turn is 360 degrees.
• The letter V makes an acute angle.

Did You Know?

Pizza slices almost always have an acute angle at the tip where you take your first bite.