Let △ABC and △CDE be equilateral triangles of the same size, and angle BCD = 80∘ between them. Find the measure of angle BAD in degrees.
+36916 Equilateral triangles, so both angles near C are 60 degrees
so angle ACD = 80 + 60 = 140 degrees
AC and CD are equal in length, so triangle ACD is isoceles
unlabelled angle A and D are equal 180 - 140 = 40 dgrees so A and D are 20 degrees each
BAD = 60 - 20 = 40 degrees
+36916 Equilateral triangles, so both angles near C are 60 degrees
so angle ACD = 80 + 60 = 140 degrees
AC and CD are equal in length, so triangle ACD is isoceles
unlabelled angle A and D are equal 180 - 140 = 40 dgrees so A and D are 20 degrees each
BAD = 60 - 20 = 40 degrees
