If the side of the rhombus ABCD is equal to the diagonal BD, then the angle ABC is.

Given:
ABCD – rhombus,
BD – diagonal,
BC = BD.
Find the degree measure of the angle ABC -?
Solution:
1. Consider a rhombus ABCD. He has all sides equal to honey, then AB = BC = CD = DA.
2. Consider a triangle ВСD. Since BC = BD, BC = BD = CD. Consequently, the BCD triangle is isosceles. So the angle DCB = angle DBC = angle CDB = 60 degrees.
3. Diagonal BD is the bisector of the angle ABC, then the angle ABC = 2 * DBC = 2 * 60 = 120 (degrees).
Answer: 120 degrees.