It has 2 congruent sides
An isosceles triangle has two congruent sides.
If it's an equilateral triangle then its 3 sides are congruent but if it's an isosceles triangle then only 2 of its sides are congruent
A right triangle can have at most 2 congruent sides, but may have no congruent sides. From the Pythagorean Theorem, the square of the hypotenuse will be equal to the sum of the squares of the other two sides - consequently the "other two sides must each be less than the length of the hypotenuse and thus not congruent with it. They can be congruent with each other however - which is what occurs in a 45°/45°/90° triangle (for any other right triangle, none of the sides will be congruent).
how many congruent sides does a scalene triangle
It has two congruent sides
An isoceles triangle has two congruent sides.
an equilateral triangle has all equal sides
any triangle has 3 sides.
An isosceles triangle has exactly two sides which are equal. (The word congruent usually applies to triangles, not sides.)