1. Triangles
6 Chapter

2. Triangle
A triangle
Edges and vertices3Schläfli symbol{3}
(for equilateral)Areavarious methods;
see belowInternal angle (degrees)60°
(for equilateral)

3. A triangle, showing exterior angle d.

4. The measures of the interior angles of
the triangle always add up to 180
degrees (same color to point out they
are equal).

5. Types of triangles
I ) Equilateral Triangle
II) Isosceles Triangle
III) Right Triangle
IV) Scalene Triangle
V) Acute Triangle
VI)Obtuse Triangle

6. Equilateral Triangle
Three equal sides
Three equal angles, always 60°

7. Isosceles Triangle
Two equal sides
Two equal angles

8. Right Triangle
Has a right angle (90°)

9. Scalene Triangle
No equal sides
No equal angles

10. Acute Triangle
All angles are less than 90°

11. Obtuse Triangle
Has an angle more than 90°

12. Basic proportionality theorem
If a line is drawn parallel to one side
of a triangle and it intersects the other
two sides in two distinct points then it
divides the two sides in the same ratio.

13. In the ,
if DE||BC, then

14. Converse of Basic Proportionality
Theorem
If a line divides any two sides of a
triangle in the same ratio, the line
must be parallel to the third side.

15. In the, if D and E are two points on
AB and AC respectively such
that,, thenDE||BC

16. MADE BY :- JOSHUA
CLASS :- X B
ROLL NO :- 10209
ADMISSION NO :- 10209