Triangles (Δ)
Work through triangle classification, triangle parts, special centers, and major theorems one concept at a time.
18 concepts in this topic
These pages help you connect triangle vocabulary to live side lengths, angle measures, centers, and theorem patterns instead of learning each idea in isolation.
Scalene Triangle
A scalene triangle has three sides of different lengths.
Isosceles Triangle
An isosceles triangle has at least two equal sides.
Equilateral Triangle
An equilateral triangle has three equal sides and three equal angles.
Acute Triangle
An acute triangle has three angles less than 90 degrees.
Right Triangle
A right triangle has one angle measuring 90 degrees.
Obtuse Triangle
An obtuse triangle has one angle greater than 90 degrees.
Equiangular Triangle
An equiangular triangle has three equal angles.
Altitude
An altitude is a perpendicular segment from a vertex to the opposite side or its extension.
Median
A median connects a vertex to the midpoint of the opposite side.
Midsegment
A midsegment connects the midpoints of two sides of a triangle.
Hypotenuse & Legs
In a right triangle, the hypotenuse is opposite the right angle and the other sides are the legs.
Centroid
The centroid is the point where the medians intersect.
Incenter
The incenter is the point where the angle bisectors intersect.
Circumcenter
The circumcenter is the point where the perpendicular bisectors intersect.
Orthocenter
The orthocenter is the point where the altitudes intersect.
Triangle Inequality
The sum of any two side lengths in a triangle must be greater than the third side.
Pythagorean Theorem
In a right triangle, a squared plus b squared equals c squared.
Exterior Angle Theorem
A triangle's exterior angle equals the sum of the two remote interior angles.