standard_description: Prove theorems about triangles. Theorems include: measures of interior angles of a triangle sum to 180°; base angles of isosceles triangles are congruent; the segment joining midpoints of two sides of a triangle is parallel to the third side and half the length; the medians of a triangle meet at a point.
problem_activity: Find all of the roots of the following quartic equation:
$${h(x)=x^4-2x^3-9x^2-18x}$$


aligns: no