The Correct Answer is (E)
— Recall that congruent means that two polygons are the same shape and size. Since ∆ABC
and ∆ACD
are congruent, you know that each angle from one triangle corresponds to an angle of the other triangle. If you are having a hard time visualizing the triangles matching up, mark up the given diagram or draw your own to show the triangles side by side:Just by filling in the angles, you can see that the remaining angle in each triangle must be 60°. To find ∠BCD, simply sum ∠BCA and ∠ACD to get a total of 60° + 90° = 150°.
