Page 12 - DMTH201_Basic Mathematics-1

Unit 1: Trigonometric Functions-I

0° 30° 45° 60° 90° Notes
Sin 0 1
1 2 3
2 2 2
Cos 1 3 2 1 0
2 2
2
Tan 0 3 1 3 undef.
3

1.2.1 Reciprocal Ratio

The reciprocal ratios are trigonometric ratios, too. They are outlined below:
cotangent x = 1/tan x = (adjacent side)/(opposite side)
secant x = 1/cos x = (hypotenuse)/(adjacent side)

cosecant x = 1/sin x = (hypotenuse)/(opposite side)

1.2.2 Rotations of Angles

Angles are also called rotations because they can be formed by rotating a ray around the origin
on the coordinate plane. The initial side is the x-axis and the ray that has been rotated to form an
angle is the terminal side.

Example:

Reference angles are useful when dealing with rotations that end in the second, third, or fourth
quadrants.

Radians

Up until now, you have probably only measured angles using degrees. Another useful measure,
based on the unit circle, is called radians.
The figure shows measures in degrees and radians on the unit circle that you should probably

memorize, as they are commonly used measures.

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