a) The students who are members of both sets can be described by
... a ∩ b
b) The students who are members of a but not b can be described by
... a ∩ b'
c) The students who are members of one or both sets can be described by
... a ∪ b
d) The students who are not in one set or not in the other set can be described by
... a' ∪ b' . . . . = (a ∩ b)'
6 acts as the base. 15 acts as the height, because it extends from the base to meet vertex opposite the base at a 90° angle.
General formula for triangle area
a = 1/2 × b × h
plug in the numbers
a = 1/2 × 6 × 15
a = 90/2
a = 45
The area of the triangle is 45 units²
