Axisymmetric figure, a mathematical term, is defined as a figure folded along a straight line in a plane, and the parts on both sides of the straight line can completely overlap.
A straight line is called the axis of symmetry, and the axis of symmetry is represented by a dotted line. At this time, we also say that this figure is symmetrical about this line. Such as circle, square, isosceles triangle, equilateral triangle, isosceles trapezoid, etc.
Theorem:
Theorem 1: Two graphs symmetric about a straight line are conformal.
Theorem 2: If two figures are symmetrical about a straight line, then the symmetry axis is the perpendicular line connecting the corresponding points.
Theorem 3: Two figures are symmetrical about a straight line. If the axis of symmetry intersects the extension lines of two symmetrical line segments, the intersection point is on the axis of symmetry.