Easy Way to Remember Formulae (Optional Mathematics)

TRIGONOMETRY 

Basic Formulae 

Now, consider right angle triangle,

Then, the reciprocal relation says that Cosec, Sec, Cot is the inverse of Sin, Cos, Tan respectively.                                                                        

Below mentioned relations are derive from Pythagoras theorem.(h² = p² + b²)

An identity involving the trigonometric ratios which is true for any value of an angle is called a trigonometric identity.

Fig: Trigonometric Table

Height and Distance

The main application of trigonometry is to find the height of an object and the distance between two objects, which are difficult to measure directly. It is widely useful in surveying, map-making, navigation and astronomy.

For this we deal two types of angles to form when the observer observes at the top or bottom of the erected object. They are angle of elevation and angle of depression.

Angle of Elevation 

The angle formed by the line of observation to the horizontal line (ground) when the observer observes the upward object, is called an angle of elevation.

Angle of Depression

The angle formed by the line of observation to the horizontal line when the observer observes the downward object is called an angle of depression.

Altitude of Sun

An angle made by the sunlight to the ground (horizontal line) is called an altitude of the sun. When any object erected on the way of the sunlight, it casts the shadow on the backward to the sun.