Minimum or maximum is determined by the first term of the equation, which is [a]. If [a] is positive, then it is a minimum equation as the parabola heads up. If [a] is negative, then it is a maximum equation as the parabola heads down.
In the given figure, line segment is constructed on the triangle parallel to line segment . ... This line can then be considered as a transversal of these parallel lines. Angle and angle are therefore corresponding angles. And as they're corresponding, this means that they're equal.
