Triangles

Do you remember a polygon with the least number of sides? That is a trianglequadrilateral.

Let us see the different types of triangles we can get.

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Naming triangles based on sides

A triangle having all three unequal sides is called a scaleneunequal triangle.

Three unequal Sides: AB, BC , CA

A triangle having two equal sides is called an IsoscelesScalene Triangle.

Two equal Sides: DE, FD

A triangle having three equal sides is called an Equilateralequal triangle.

Three equal Sides: XYZ

A triangle having all three unequal sides is called a Scalene Triangle.

A triangle having two equal sides is called an Isosceles Triangle.

A triangle having three equal sides is called an Equilateral Triangle.

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Naming triangles based on angles

If each angle is less than 90°, then the triangle is called an acute angled triangle.

If any one angle is a right angle then the triangle is called a right angled triangle.

If any one angle is greater than 90°, then the triangle is called an obtuse angled triangle.

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Let's carry out an activity : you can move the vertices

Do you observe anything? Some of the facts that you may have noticed may include that:

You can move around vertices A,B,C and observe the change in angle measure.

• All unequal Sides: AB, BC , CA

• When a triangle has all the equal angles, then its sides are also equalnot equal.

+ Also if a triangles has all the three sides as equal, then its angles are also equalnot equal.

+ If two sides of a triangle are equal, then it also has twothree equal angles and if the two angles of a triangle are equal, then it has twothree equal sides.

+ If the three sides of a triangle are unequal then the three angles are also unequalequal .

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