Equilateral

TRIANGLES (tri- means 3). • Triangles ALWAYS have 3 sides. • The interior angles of a triangle add up to 180 degrees. • There are following types of triangles: – Equilateral Triangle – Isosceles Triangle – Right- Angled Triangle – Scalene Triangle We will learn about Equilateral Triangle.

Equilateral Triangle • An equilateral triangle has got 3 sides of equal length and 3 angles that are equal. • Since ALL the angles in a triangle add up to 180º then 180 divided by 3 must be 60º.

EQUILATERAL TRIANGLE

• Construction • Properties

STEP 1

Draw a straight line AB of 5cm. A

5cm

B

STEP 2

A

5cm

B

Open the compass for 5cm and make an arc from B.

STEP 3 C

A

5cm

B

Intersect the arc with the same compass at point C from A.

STEP 4 C

A

5cm

B

Join the intersection point with both of ends.

STEP 5 The Equilateral Triangle ABC is ready. Here-

C 60° m

5c m

5c

Sides AB=BC=AC=5cm &

60° A

60° 5cm

B

Angles ∠ABC= ∠BCA= ∠ CAB=60°

Properties of Equilateral Triangle • All side are equal. • Angles of every equilateral triangle are equal to 60°. • Every altitude is also a median and bisector. • Every median is also an altitude and bisector. • Every bisector is also an altitude and median. BACK NEXT

• References – Text Book – www.icteachers.co.uk.

• Subject Teacher – Mrs. Jatinder Kaur

• Prepared By – Gagandeep Kaur (9TH ) – Harsimran Kaur (9TH )

• Edited By – Computer Staff END