Find the size of angle CFD?

Question

Draw triangle ABC so that angles A and B are both 42 degrees. Why should AB be longer than BC? Extend CB to E, so that CB = BE. Mark D on AB so that DB = BC, then draw the line ED, which intersects AC at F. Find the size of angle CFD.

Answer 1

<C is 180 - 42 - 42 = 96 degrees.

side AB is opposite angle C and BC is opposite angle A. Since side opposite larger angle is always larger in a triangle, then AB is longer than BC.