Diagonal angle refers to the internal angle between two sides in a triangle, which is called the diagonal of the third side.

Diagonal introduction:

Inner corner, opposite side refers to the side opposite to an angle. Angle is a mathematical concept, which can describe the size of angle, that is, the amount that must be rotated when any one of two intersecting lines overlaps with another intersecting line. The unit of angle is degree, and degree is the unit to measure the size of angle. A fillet is divided into 360 equal parts, and each part is defined as 1 degree (1 degree).

Equiangular introduction;

A theorem of shape, in the same triangle, if two sides are equal, the diagonals of the two sides are equal, that is, equilateral and equilateral, such as isosceles right triangle, which is the inverse theorem (axiom) of equilateral.

Also known as the Latin Pons asinorum theorem, also known as the isosceles triangle theorem, is a mathematical theorem in Euclidean geometry, which means that the two sides of an isosceles triangle correspond to the same two base angles. The isosceles triangle theorem is also the content of proposition 5 in volume 1 of Euclid's Geometry.

Equiangular equilateral introduction:

In the same triangle, if two angles are equal, then the opposite sides of the two angles are equal. Usually used to prove isosceles triangle. Inverse theorem of equilateral and equal angle. The properties of equilateral and equilateral have been studied in the thirteenth chapter of eighth grade mathematics of People's Education Press.

Parallelogram properties:

If the quadrilateral is a parallelogram, then the two opposite sides of the quadrilateral are equal respectively; If the quadrilateral is a parallelogram, then the two opposite corners of the quadrilateral are equal.

If a quadrilateral is a parallelogram, then the adjacent angles of this quadrilateral are complementary; The parallel segments between two parallel lines are equal; If a quadrilateral is a parallelogram, then the two diagonals of the quadrilateral are equally divided.

Parallelogram judgment:

If two opposite sides of a quadrilateral are equal, then the quadrilateral is a parallelogram; If a set of opposite sides of a quadrilateral are parallel and equal, the quadrilateral is a parallelogram; If the two diagonals of a quadrilateral are bisected, then the quadrilateral is a parallelogram.

If the two diagonals of a quadrilateral are equal, then the quadrilateral is a parallelogram; If two opposite sides of a quadrilateral are parallel, then the quadrilateral is a parallelogram.