# Some Basic Types and Results of Triangles

**1. **An angle whose measurement is of is called a **RIGHT ANGLE.**

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

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

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

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

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

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

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

**9. **A triangle whose sides are of equal length is called an **EQUILATERAL TRIANGLE.**

**10. **A triangle whose two sides or two angles are equal measurements is called an **ISOSCELES TRIANGLE.**

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