ೃ⁀➷ 𝐄𝐦𝐚𝐭𝐡: 𝐓𝐫𝐢𝐚𝐧𝐠𝐥𝐞𝐬

Triangles is a plane closed figure formed by three line segments. It has three angles and three sides. The angles in a triangle are called vertices (plural for vertex). 

• Exterior angle: the angle that is formed with one side and the adjacent extended side of a triangle. There are 3 exterior angles in a triangle and the sum of the exterior angles of a triangle is always equal to 360°.

• Right triangle: triangle in which one angle is a right angle. The two sides that form the right angle are called legs, while the remaining side which is opposite the right angle is called the hypotenuse.
  The Pythagorean theorem states that “The square of the hypotenuse in a right angle triangle is equal to the sum of the squares of the two legs.”
  Two types of right triangles:
  1. 30°-60°-90° Triangle — is a right triangle whose acute angles measure 30° and 60°.
  2. Isosceles Right Triangle — a triangle with two equal sides known as the legs, a right angle, and two acute angles which are congruent to each other. 

• Equilateral triangle: a triangle that has all its sides equal in length. The sum of the three angles is 180°, each angle measures 60°.

• Altitude of a triangle is the perpendicular line segment that connects a vertex of the triangle to the line containing the opposite side. 

• According to sides, scalene has no two equal sides. Isosceles has two sides of the same length. Equilateral has equal sides. 

• According to sides, acute triangle has all angles less than 90. Right triangle has one angle 90, obtuse triangle has one angle that measures more than 90, and equiangular triangle has all angles equal. 

• [NOTE: Base is the opposite of vertex]