How can you prove a triangle is isosceles? (4 points)
use the distance formula to see if at least two sides are congruent.
use the slope formula to see if any sides are perpendicular.
use the distance formula to see if all three sides are congruent.
use the slope formula to see if any sides are parallel.

To prove a triangle is isosceles, it can be used the distance formula to see if at least two sides are congruent.

Step-by-step explanation:

An isosceles triangle is a triangle in which two sides are equal in length. The sides are called equal sides, and the last side unequal to them is called the base. By definition, every regular triangle is also isosceles, but the converse is not true.

If a triangle has two equal sides, then these sides are called the lateral sides, and the third side is called the base. The angle formed by the sides is called the vertex angle, and the angles, one of the sides of which is the base, are called the corners at the base.

A triangle with two equal sides has one axis of symmetry, which passes through the vertex angle and the middle of the base. This axis of symmetry coincides with the bisector of the vertex angle, the median drawn to the base, the height drawn from the vertex corner and the middle perpendicular.