Triangle ABC: side AB 9 cm, side AC 12 cm, angle B = 100 °, angle C = 50 °: find the area ABC.

To do this, we will use the formula for finding the area of a triangle on two sides and the angle between them: the area of a triangle is half the product of two sides multiplied by the sine of the angle between them. s = 1 / 2ab * sin of the angle between them. Initially, we find the angle between the sides, we know two angles, since the sum of all angles = 180 degrees, we find the angle between the known sides:
1) 180- (100 + 50) = 30 degrees
2) S = 1/2 9 * 12 * sin 30
S = 54 * sin30 (sin 30 = 1/2)
S = 54 * 1/2
s = 27 square centimeters
Answer: s = 27 sq.