2. The common endpoint of an angle is called point of intersection.

3. An angle that measures exact 90 degrees is a right angle.

4. Acute angle measures more than 90 degrees but less than 180 degrees.

5. Protractor is an instrument used to measure the angle.

6. A triangle has three sides, 3 angles and three vertices.

7. The sum of the length of the two sides of a triangle is always less than the length of the third sides.

8. A quadrilateral is a figure with 4 sides, angles and vertices.

9. When you joined 2 triangles with their common length, you can form a quadrilateral.

10. The hands of the clock above shows acute angle.