Book- ML Aggarwal
Board- ICSE
Publication- Avichal
Chapter- Trigonometric Identities
Chapter number-18
If A is an acute angle and sin A = 3/5, find all other trigonometric ratios of angle A (using trigonometric identities).
Q no. 1, M L Aggarwal, trigonometric identities
We have been given that
sin A = 3/5 and A is an acute angle
So, in ∆ABC we have ∠B = 90o
And,
AC = 5 and BC = 3
By Pythagoras theorem,
AB = √(AC2 – BC2)
= √(52 – 32) = √(25 – 9) = √16
= 4
Now,
cos A = AB/AC = 4/5
tan A = BC/AB = 3/4
cot A = 1/tan θ = 4/3
sec A = 1/cos θ = 5/4
cosec A = 1/sin θ = 5/3