Q. 26 A

If 3 cot A = 4, check whether =cos2A–sin2 A or not.

Answer :

Given: 3cot A = 4

We know that,



Side adjacent to angle A =AB = 4k

The side opposite to angle A =BC = 3k

where k is any positive integer

Firstly we have to find the value of AC.

So, we can find the value of AC with the help of Pythagoras theorem

(AB)2 + (BC)2 = (AC)2

(4k)2 + (3k)2 = (AC)2

(AC)2 = 16 k2 + 9 k2

(AC)2 = 25 k2

AC =25k2

AC = ±5k [taking positive square root since, side cannot be negative]




And RHS = cos2 A – sin2 A



From Eqs. (i) and (ii) LHS =RHS

Hence Proved

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Champ Quiz | Trigonometric Identities33 mins
Trigonometric Identities33 mins
NCERT | Trigonometric Identities52 mins
Quiz | Task on Trigonometric Ratios46 mins
Algebraic Identities48 mins
Quiz | Practice Important Questions on Trigonometrical Identities46 mins
Quiz on Trigonometric Ratios31 mins
T- Ratios of Specified Angles58 mins
Trick to learn all Trigonometric Formulae28 mins
Testing the T- Ratios of Specified Angles57 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses