For a summary on triangles in Class 6 ICSE Maths, we’ll cover the basic concepts:

1. **Definition of a Triangle**: A triangle is a closed figure with three sides.

2. **Types of Triangles**: Triangles can be classified based on sides and angles:

– Based on sides:

– Scalene Triangle: All sides are of different lengths.

– Isosceles Triangle: Two sides are of equal length.

– Equilateral Triangle: All sides are of equal length.

– Based on angles:

– Acute-angled Triangle: All angles are less than 90 degrees.

– Right-angled Triangle: One angle is 90 degrees.

– Obtuse-angled Triangle: One angle is greater than 90 degrees.

3. **Properties of Triangles**:

– The sum of angles in a triangle is always 180 degrees.

– The exterior angle of a triangle is equal to the sum of the two interior opposite angles.

– The sum of the lengths of any two sides of a triangle is greater than the length of the third side.

4. **Pythagorean Theorem**: In a right-angled triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the other two sides.

5. **Area of a Triangle**: The area of a triangle is given by the formula A = 1/2 × base × height, where base and height are perpendicular to each other.

6. **Similarity of Triangles**: Two triangles are similar if their corresponding angles are equal and their corresponding sides are in proportion.

This summary covers the basics of triangles in Class 6 ICSE Maths.