CBSE Notes, Lectures

CBSE - Mathematics - Introduction to Trigonometry

Introduction to Trigonometry

NCERT Exercise Exercise 8.1

Given sec θ = 13/12, calculate all other trigonometric ratios.


 

Let ΔABC be a right-angled triangle, right-angled at B.

We know that sec θ = OP/OM = 13/12   (Given)
Let OP be 13k and OM will be 12k where k is a positive real number. 
By Pythagoras theorem we get,
OP2 = OM2 + MP
(13k)2 = (12k)+ MP
169k2 - 144k2 = MP2
MP2 = 25k2

MP = 5

Now,

sin θ = MP/OP = 5k/13k = 5/13

cos θ = OM/OP = 12k/13k = 12/13

tan θ = MP/OM = 5k/12k = 5/12

cot θ = OM/MP = 12k/5k = 12/5

cosec θ = OP/MP = 13k/5k = 13/5

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