Write the word “isosceles” and add

Write the word “isosceles” and add it to the phrase: “a small red isosceles triangle”. Ask the children to remove all the triangles which are not isosceles. The triangle which a child brings is still not the one you want so you give the last clue. Write the word “right” and add it to the phrase: “a small red isosceles right triangle”. Now there is only one triangle which will fit the description. Place the triangle with the phrase. Then transpose the phrase and see how it makes sense.