The three-line segments or the three sides which enclosed to form a shape called triangle and it forms the sides of the triangle. In learn three sides the lengths of the sides are always proportional to their opposite angles. The sum measures of the two sides which is always greater than the third side.

The triangle is the main part of the geometry which deals with the sides. Let us learn three sides of the triangle according to their length of the sides.

**Three sides are Equal:**

The three sides of a triangle are having the same measurements; it is called as equilateral triangle. The triangle consists of angles which measures 60° in all of its vertices's.

**Only two sides are equal:**

When two sides of a triangle are equal in its measurements, then that triangle is referred to as an isosceles triangle .In this triangle, the two sides are congruent with each other.

**Three sides are unequal:**

When three sides are unequal in its measurement, then it is called as a scalene triangle and the three angles are also different.

**Example 1:**

In a given triangle ABC, the two angles of a triangle measures about 70° and 50°. Find the third angle.

**Solution:**

In ΔABC ∠B = 70°, ∠C = 50°

∴∠B + ∠C = 70° + 50° = 120°

Now, by the property of a triangle that is three angles are together equal to two right
angles.

∠A + ∠B + ∠C = 180°

∴ ∠A = 180° - 120° = 60°

**Example 2:**

Each of the two equal angles of an isosceles triangle is twice the third angle. Find the angles of the triangle in learn three sides.

**Solution:**

Let the measure of the smallest angle be x. Then each of the other angles has a measure of 2x. Thus the sums of the three angles of a triangle which can be given as in learn three sides.

The sum of angles = x°+2 x° + 2 x° = 5 x° = 180°

(Sum of three angles of a triangle = 180°)

∴ 5 x°= 180°

x° = 180°/5 = 36°

Thus the other two angles 2 × 36° = 72°