Angle is measurement of inclination of two lines. The angles that are inside a shape are knows as interior angles. On the other hand, the exterior angle is an angle that is outside of the shape.

TYPES OF ANGLES

Angles can be classified as acute angle, right angle, obtuse angle, straight angle and reflex angle.

Acute Angles

Acute angles are angles, whose measurement is less than 90° and more than 0°.

Right angle

An angle whose measure is 90° is called a right angle. The angle between the lines \(x\) and \(y\) is 90° and these lines are said to be perpendicular lines.

Obtuse Angles

Obtuse angles are angles, whose measurement is more than 90° and less than 180°. 

Straight angle

An angle of 180° is known as straight angle.

Reflex angle

An angle, whose magnitude is more than 180o and less than 360o, is known as reflex angle.

Complementary angles

Two angles whose sum is 90° are known as complementary angles. If \(\alpha \)and \(\beta \) are complementary angles, then \(\alpha  + \beta  = {90^ \circ }\)

Supplementary angles:

Two angles whose sum is 180° are known as supplementary angles. If \(\alpha \) and \(\beta \) are supplementary angle, then

\(\alpha  + \beta  = {180^ \circ }\)

4 right angles = 360° = 400 grades = \(2\pi \,\) radians

Angles associated with parallel lines:

Vertically opposite angles, Corresponding angles, alternate angles are explained by this diagram.

In this diagram

\(b = a\), \(c = d\), \(n = q\), \(m = p\)  (Vertically opposite angles)

\(b = n\)  (Corresponding  angles)

\(d = p\)  (Alternate angles)