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## Angles & Rotations ### Zero angle - If the ray OA has zero rotation; that is, it does not rotate, the initial arm itself is a terminal arm, and the angle so formed is zero angle. - $m(\angle AOB) = 0^o$ ### One rotation angle: complete angle - After one complete rotation, if the initial ray O...

## Angles & Rotations ### Zero angle - If the ray OA has zero rotation; that is, it does not rotate, the initial arm itself is a terminal arm, and the angle so formed is zero angle. - $m(\angle AOB) = 0^o$ ### One rotation angle: complete angle - After one complete rotation, if the initial ray OA coincides with the terminal ray OB, then the angle so formed is known as one rotation angle. - $m(\angle AOB) = 360^o$ ### Straight angle: - After the rotation, if the initial ray OA and the terminal ray OB are in opposite directions, then the directed angle so formed is known as a straight angle. - $m(\angle AOB) = 180^o$. ### Right angle: - One fourth of one rotation angle is called one right angle. It is also half of a straight angle. One rotation angle is four right angles. ### Angles in Standard position - In the rectangular coordinate system, a directed angle with its vertex at origin O and the initial ray along the positive X-axis is called an angle in standard position. ### Angle in a Quadrant - A directed angle in standard position is said to be in a particular quadrant if its terminal ray lies in that quadrant. ### Quadrantal Angles - A directed angle in standard position, whose terminal ray lies along one of the axes, is called a quadrantal angle. These angles are multiples of 90°. ### Co-terminal angles - Directed angles of rotation having the same initial rays and terminal rays are called co-terminal angles. These angles are multiples of 360°.