 Let us recall the properties of equilateral triangle and isosceles triangle. An equilateral triangle is shown on the left and the triangle is triangle ABC. And when we say it is an equilateral triangle that means all the sides of the triangle are equal. They could be of any length but all of them are equal. So AV is equal to BC is equal to AC. One more interesting property of an equilateral triangle is that all the angles of equilateral triangle are equal as well and they are all of the same measure and they are all 60 degrees. So angle ABC is equal to angle BCA is equal to angle CAB and all are equal to 60 degrees. On the right hand side we have triangle PQR and it is an isosceles triangle as we can see. Isosceles triangle because by definition two of the sides of triangle PQR are equal. So whenever two sides of any triangle are equal in length it is called as an isosceles triangle and in this case PQ is equal to PR. They could be of any length and now another interesting property of an isosceles triangle is that the angles opposite to the equal sides are also equal. So angle PRQ is opposite side PQ and angle PQR is opposite to the side PR and therefore these are equal. So angle PQR is equal to angle PRQ. In equilateral triangle we just saw that all the angles are 60 degrees that is not the case in isosceles triangle. So the measures of these angles can be anything but they are acute angles. There is an interesting note that I would like to share with you. The equilateral triangle is an isosceles triangle because by definition if all three sides are equal at least two sides are equal as well and therefore every equilateral triangle is by default an isosceles triangle but vice versa is not true that means every isosceles triangle is not an equilateral triangle.