In a parallelogram, opposite sides are equal and parallel, which is a defining property.

All polygons are defined as closed figures formed by a finite number of line segments.

In a regular polygon, all sides and all interior angles are equal.

An isosceles triangle is defined as having at least two sides that are equal in length.

Similar triangles have equal corresponding angles, but their sides are in proportion, not necessarily equal.

A regular polygon is defined as a polygon with all sides and angles equal, and it cannot be concave; it must be convex.

A circle is defined as a round shape with no corners.

A convex polygon cannot have curved sides; all sides must be straight.

While a parallelogram has opposite sides and angles that are equal, it does not necessarily have all angles as right angles unless it is a rectangle.

In a regular polygon, all sides and angles are equal, and the vertices are convex, not concave.

In a rhombus, while all sides are equal and diagonals bisect each other at right angles, the diagonals are not necessarily equal in length.

In a square, all angles are right angles (90 degrees), not acute.

An isosceles triangle has two equal sides and the angles opposite those sides are equal, but it does not have all angles equal unless it is also equilateral.

Polygons are defined as shapes made up of straight line segments, so having curved sides disqualifies a shape from being a polygon.

Not all triangles have all angles acute; for example, a right triangle has one angle that is 90 degrees.

A quadrilateral is a four-sided figure and not a type of triangle.

Complementary angles are two angles whose sum is 90 degrees. All the given pairs meet this criterion.

Adjacent angles are defined as angles that share a common vertex and a common side.

Adjacent angles are defined as angles that share a common vertex and a common side.

Supplementary angles are two angles that add up to 180 degrees. An acute angle (less than 90 degrees) and an obtuse angle (more than 90 degrees) can add up to 180 degrees.

The distance from the origin to a point (x, y) is given by √(x² + y²). The point (0, 1) has a distance of 1, which is the smallest.

The point (2, 3) is the midpoint of the segment joining (1, 2) and (3, 4), making it equidistant from both.

Substituting x = 2 into the equation y = 2(2) + 1 gives y = 5, so the point (2, 5) lies on the line.

A concave hexagon has at least one interior angle greater than 180 degrees, which makes it a non-convex polygon.

The number of diagonals in a polygon is given by n(n-3)/2. For a hexagon (n=6), it has 9 diagonals, which is more than the others.

A star-shaped polygon has at least one interior angle greater than 180 degrees, making it concave.

A star-shaped polygon is an example of a non-convex polygon because it has points that point inward.

A concave hexagon has at least one interior angle greater than 180 degrees, making it a non-convex polygon.

A rhombus has all sides equal and opposite angles equal.

In a rectangle, the diagonals are equal in length but not perpendicular.