The RD Sharma Solutions for Class 7 Maths Chapter 15 properties of triangles deal with many sub-topics that can be very useful for the students in understanding higher grade mathematics. Firstly, a triangle is nothing but a closed two-dimensional shape that has three straight sides. And the region which is formed by the triangle is termed a triangular region. In this chapter, the students learn about the sides, angles, and elements of the triangles. Along with this, the interior and exterior angles of it are also discussed.
So, there are three types of triangles based on their lengths. They are the scalene triangle, isosceles triangle, and equilateral triangle. All the sides and angles of the scalene triangle are unequal, whereas all the equilateral triangle sides are equal and make 60° to each other. Isosceles triangles are the ones that have at least two equal sides.
Other than these types, there is another way of separating triangles that is by measurement of angles. Based on this, there are three types. They are the Acute triangle, Right triangle, and Obtuse triangle. An acute triangle is made when all the three internal angles of the triangle are acute, i.e., they make less than 90°, while an obtuse triangle is made when one of the interior angles makes more than 90°, and the sum of the remaining two angles is less than 90 degrees. Finally, a right triangle is made when two sides make 90° to each other.
Another concept, the perimeter of a triangle, is the sum of all its three sides. Meanwhile, the angle sum property of a triangle states that the sum of interior angles of a triangle is 180°. Along with them, exterior and interior opposite angles of a triangle are also included in the curriculum. Another important concept called triangle inequality property is also being discussed.
More importantly, the Pythagoras theorem is taught to the students. It states that, The square of the hypotenuse side of a right-angled triangle is the sum of the squares of the other two sides. Furthermore, the Converse of Pythagoras theorem and Pythagorean triplet is also taught in this chapter.