Triangle abc is an equilateral triangle with side lengths labeled a, b, and c. triangle a b c is an equilateral triangle. the length of side a b is c, the length of b c is a, and the length of a c is b. trigonometric area formula: area = one-half a b sine (c) which expressions represent the area of triangle abc? select three options. a c sine (60 degrees) one-half b c sine (60 degrees) one-half a squared sine (60 degrees) startfraction a squared b sine (60 degrees) over 2 endfraction startfraction a b sine (60 degrees) over 2 endfraction