Triangle A B C is shown. The length of B C is a, the length of A C is b, and the length of A B is c. Auxiliary lines are added from point B to point D and point C to point D to form a right angle. See the figure of ΔABC with auxiliary lines added. If c is the base of ΔABC, the height is . sin(A) = . The previous statement is leading to the derivation of which area formula? Area ΔABC =