**1. **The angle whose measurement is of is called **RIGHT ANGLE.**

**2. **The angle whose measurement is greater than is called **OBTUSE ANGLE.**

**3. ** The angle whose measurement is less than is called **ACUTE ANGLE.**

**4. **If , and are the midpoints of the sides of , then , and are called **Medians **of the triangles and medians of a triangles are concurrent at the point

**5. **If , and are the perpendiculars from , , to the sides , and of respectively, then , and are called **ALTITUDES OF THE TRIANGLE.**

**6. **The line passing through the mid points of the sides of , and perpendicular to the respective sides are called **RIGHT BISECTORS OF THE TRIANGLE.**

**7. **Angle bisector of a triangle are concurrent at .

**8. **The triangle whose one angle is is called a **RIGHT ANGLED TRIANGLE.**

**9. **The triangle, whose sides are of equal length, is called **EQUILATERAL TRIANGLE.**

**10. **The triangle whose two sides or two angles are equal of measures, is called **ISOSCELES TRIANGLE.**

**11. **If , and are the internal angles of a triangle then