*Trigonometry*:

In a right angled OAB, where BOA = ,

Some Important Points To remember:

tanQ = Perpendicular/Base = AB/OA.

SinQ = Perpendicular/Hypotenuse = AB/OB.

CosQ = Base/Hypotenuse = OA/OB.

Easy Way to Remember the above is

S C T

P B P

H H B

Sona | Chindi | Tol

Pandit | Badri | Parsad

Har | Har | Bola.

*2. Trigonometrical Identities:*- sin
^{2}+ cos^{2}= 1. - 1 + tan
^{2}= sec^{2}. - 1 + cot
^{2}= cosec^{2}. Suppose a man from a point O looks up at an object P, placed above the level of his eye. Then, the angle which the line of sight makes with the horizontal through O, is called the*Angle of Elevation:**angle of elevation*of P as seen from O.

Angle of elevation of P from O = AOP.Suppose a man from a point O looks down at an object P, placed below the level of his eye, then the angle which the line of sight makes with the horizontal through O, is called the*Angle of Depression:**angle of depression*of P as seen from O.