 ## Fourth grade math - Acute, right, obtuse, and straight angles

Angles are classified into 5 groups depending on the angle measurement. Acute angle means, it measures less than 90 degrees. If it measures 90 degress, it is a right angle and so on. You will learn more about angles and to solve problems related to angles by using the resouces on this page which include measuring angles worksheet, complementary and supplementary angles worksheet.

### Related Topics

• #### What are the different types of angles?

• In geometry, there are three types of angles:
acute angle-an angle between 0 and 90 degrees.
right angle-an 90 degree angle.
obtuse angle-an angle between 90 and 180 degrees.
straight angle-a 180 degree angle.

• #### What is the acute angle?

• The acute angle is the small angle which is less than 90°. If you choose the larger angle you. will have a Reflex Angle instead: The smaller angle is an Acute Angle, but the larger angle is a Reflex Angle.

• #### What is acute and obtuse angle?

• An acute triangle is a triangle with all three angles acute (less than 90°). An obtuse triangle is one with one obtuse angle (greater than 90°) and two acute angles. Since a triangle’s angles must sum to 180°, no triangle can have more than one obtuse angle.

• #### What is a complete angle?

• Angles larger than a straight angle but less than 1 turn (between 180° and 360°) are called reflex angles. An angle equal to 1 turn (360° or 2π radians) is called a full angle, complete angle, or a perigon. Angles that are not right angles or a multiple of a right angle are called oblique angles.

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