Geometry
Geometry is a branch of mathematics that studies the sizes, shapes, positions angles and dimensions of things.
Flat shapes like squares, circles, and triangles are a part of flat geometry and are called 2D shapes. These shapes have only 2 dimensions, the length and the width.Solid objects are also known as 3D objects having the third dimension of height or depth.
Angles in Geometry:
In geometry, an angle can be defined as the figure formed by two rays meeting at a common end point. An angle is represented by the symbol ∠.
Types of Angle:

 Acute Angle
An Acute angle (or Sharp angle) is an angle smaller than a right angle ie. it can range between 0 – 90 degrees.

 Obtuse Angle
An Obtuse angle is more than 90 degrees but is less than 180 degrees.

 Right Angle
An angle of 90 degrees.

 Straight Angle
An angle of 180 degrees is a straight angle, i.e. the angle formed by a straight line