Properties of a perpendicular drawn from the point of intersection of two equal sides of an Isosceles Triangle:
a)
It bisects the base.b)
It bisects the angle.c)
It is perpendicular to the base. Note: If the perpendicular drawn in an Isosceles Triangle satisfies any one of the three properties/conditions then the other two will
necessarily be true.
Since, AB=AC therefore the Point of Intersection of these two sides is Point A
Option I says
∠B = 45°: This only tells us that ∠C = 45. But nothing about the line AK. It could be a perpendicular but it's not necessary based on the information given. If it's not the perpendicular then it won't bisect the ∠A.
FALSE
Option II says
K is the midpoint of BC: If K is the midpoint of BC it means Line AK is bisecting the Line BC which satisfies one of the three properties/conditions. Therefore, Line AK is perpendicular to the base and will bisect the ∠A.
TRUEOption III says
AK is the altitude to the base BC: It directly states that Line AK is perpendicular to the base. Therefore, it will bisect the ∠A.
TRUE Only options II and III satisfy the above mentioned conditions. (D)