A triangle that is isosceles has at least two of its sides equal. We can draw an isosceles triangle and understand the two sides of an isosceles triangle which are equal in length. Suppose it as b and the remaining side of length denoted as a. In a triangle, this property is said to be equivalent as the two angles also become equal. A triangle that is isosceles has both sides as equal and have two equal angles.

An obtuse triangle is called obtuse by the fact that one of the angles in the triangle is an obtuse angle.

**Isosceles Triangle**

A triangle which is isosceles is a type of triangle that has any of the two sides equal in length. In the isosceles triangle, the two angles are opposite to equal sides and are equal in measure. We can write as triangles are of three types based on their sides as mentioned below:

- A Scalene triangle has all three sides that are unequal.
- An Isosceles triangle has only two sides that are equal.
- An Equilateral triangle has all three sides that are equal.

**Properties of Isosceles Triangle**

- In a triangle the two sides are said to be equal; the unequal side is known as the base of the triangle.
- The angles which are opposite to the two sides that are equal to the triangle are always equal.
- In an isosceles triangle, the altitude triangle is measured from the base to its vertex.
- A triangle that is right isosceles has the third angle of 90 degrees.

**Theorem of Isosceles Triangle:**

In an isosceles triangle as per the theorem if two sides are said to be congruent then the opposite angles to the two sides are also said to be congruent.

If there are two angles alternatively then they are congruent in a triangle which is isosceles. The sides are known to be opposite and they are also congruent.

Imagining a triangle and naming it as ABC to its three sides respectively.

So here AB = AC.

And the ∠ABC = ∠ACB.

**Obtuse Triangle**

An obtuse angle can be defined as a triangle whose any one of the angles is an obtuse angle or we can say more than 90 degrees then the angle is known as an obtuse or an angled triangle or obtuse triangle. The property is the sum of the angles that are interior angles of the obtuse triangle is equal to 180 degrees. This concludes that the angle sum property for any triangle remains unchanged.

There are a few special facts about the triangle:

- A triangle that is equilateral can never be obtuse. We can say so as an equilateral triangle has all its sides as equal and angles equal as well. And the measure of each angle is 60° which is acute. Therefore we need to note that an equilateral angle can never be an obtuse-angled triangle.

- On the opposite side of a triangle, the obtuse angle is the longest.

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