### Trigonometry - Basic concepts

Trigonometry (whose term derives from the Greek τριγωνοϛ trigōnos "triangle" and μετρον metron "measure") is a branch of mathematics that deals with ...

### Congruent angles

Α and β are said to be congruent angles if they measure the same. These have wide application in the similarity and congruence of ...

### Reference angle

A reference angle is a positive acute angle representing an angle θ of any measurement. This is the smallest angle formed ...

### Alternate angles

Alternate angles are a set of angles not adjacent to either side of a cross line. It intersects two lines (generally parallel) ...

### Vertical angles

In general, vertical angles are those angles opposite each other when two lines intersect. These are always consistent. Definition Vertical angles are ...

### External angle

In general, an angle outside, outside or angle outside a polygon is one that is between one side of a polygon and the line ...

### Internal angle

In general, an interior or interior angle is an angle within a polygon. This and the exterior angle at the same vertex are ...

### Adjacent angles

An angle is the part of the plane between two rays that have a common origin. The rays are called sides and the origin ...

### Supplementary angles

Suppose we have two angles α = 60⁰ and β = 120⁰; If we add them together it gives us 180⁰, therefore we say ...

### Complementary angles

Suppose we have two angles: If we add them together, it gives us 90⁰, therefore, we say that α and β “complement each other”, that is, ...