22 Nov 2015

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Basics Of Trigonometry

Questions Based on Trigonometry is asked in almost all the competition exams like CAT,SSC,Banking, and many more. In this Post we will discuss this Topic from basics.


This is a branch of maths that deals with the ratios between the sides of a right-angled triangle with reference to acute angle or any angle in triangle.Trigonometry literally means three angle measure.

Some Important Points To remember:

tanQ = Perpendicular/Base.

SinQ = Perpendicular/Hypotenuse.

CosQ = Base/Hypotenuse.

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


Sin2Q + Cos2Q = 1

Sec2Q - Tan2Q = 1

Cosec2Q - Cot2Q = 1


Sec2Q = 1/Cos2Q
Cot2Q = 1/Tan2Q
Cosec2Q = 1/Sin2Q

While solving important points to keep in mind,

Sin(90-Q) = CosQ,

Tan(90-Q) = CotQ,


  1. Sign in First Quadrant i.e 0<Q=<90,   will be Positive.

  2. Sign in Second Quadrant i.e 90<Q=<180, only SinQ and CosecQ will be Positive,

  3. Sign in Third Quadrant i.e 180<Q=<270, only TanQ and CotQ will be Positive,

  4. Sign in fourth Quadrant i.e 270<Q=<360, only CosQ and SecQ will be positive,

As shown In Figureast

In this Picture To remember the above sign convention a easy and lucid way is give:

ALL                                           SCHOOL                           TO                                     COLLEGE
(all trigo function positive) (only SinQ and CosQ +) (only tanQ and CotQ +) (only CosQ and SecQ +)

Below is Table For Value of Trigonometry functions:



One more Important Point is add 360 to the angle the trigonometry function does not change.

i.e,  tan(360+Q) = tanQ

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