INTRODUCTION TO TRIANGLES

​Triangles
(Congruency)

By Binita Bora

Scalene Triangle: All the side are unequal.
Isosceles Triangles: Any two sides are equal.
Equilateral Triangle: All the sides are equal.(all the angles of 60 degrees).

​On the basis of Sides

Acute Angled Triangle : All the angles are acute(<90 degrees)
Right Angled triangle: One of the angle is right angle (=90 degrees).
Obtuse Angled Triangle: One of the angle is obtuse (>90 degrees).

​On the basis of Angles

Types of triangles

Multiple Choice

Which set of the triangles are isosceles?

• A, B, C

• A, D, E, F

• A, D, F, G

• A,F, H, G

Congruency

​Two or mores shapes are congruent if they have the same size and shape.

Multiple Select

Select the congruent shapes.

• P

• Q

• R

• S

• M

Congruency of Triangles

​Two triangles are called congruent if its all corresponding sides and angles are equal.

Multiple Choice

What is the symbol of congruency of two triangles ?

• $$\equiv$$

• $$\cong$$

• $$\approx$$

• $$\sim$$

Multiple Choice

$$If\ \Delta IOP\ \cong\Delta QWE,\ then\$$

• $$\angle Q=\angle P$$

  $$\ \angle W=\angle O$$

  $$\ \angle E=\angle I$$

• $$\angle Q=\angle I$$

  $$\ \angle W=\angle O$$

  $$\ \angle E=\angle P$$

• $$\angle Q=\angle O$$

  $$\ \angle W=\angle P$$

  $$\ \angle E=\angle I$$

Multiple Select

Select the pairs of congruent triangles.

• A $$\cong$$ B

• F $$\cong$$ D

• H $$\cong$$ C

• G $$\cong$$ A

• E $$\cong$$ C

Poll

If all the dimensions of triangles are not given, Can we still know which of them are congruent?

• Yes

• NO

• Yes, with some conditions.

Criteria for congruency

SSS: Side-Side-Side
SAS : Side-Angle-Side
ASA : Angle-Side-Angle
AAS : Angle-Angle-Side
RHS : Right angle-Hypotenuse-Side

Multiple Choice

If the two triangles are congruent by SSS. Does that mean, their corresponding angles are also congruent (equal)?

• Yes

• No