Book: NCERT - Mathematics
Chapter: 8. Introduction to Trigonometry
Subject: Maths - Class 10th
Q. No. 7 of Exercise 8.1
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7
If 
evaluate:
(i) 
(ii) 
Let us consider a right triangle ABC, right-angled at point B
Cot 
= 
= 
If BC is 7k, then AB will be 8k, where k is a positive integer.
Applying Pythagoras theorem in ΔABC, we obtain
AC2 = AB2 + BC2
= (8k)2 + (7k)2
= 64k2 + 49k2
= 113k2
AC = 
k
Sin 
= 
= 
= 
Cos θ = 
= 
= 
(i) 
= (1 – sin2 θ)/(1 – cos2 θ)
= 
= 
= 
(ii) Cot2 θ = (cot θ)2
= (
2 = 
13
