Question

If sin θ = 3/5 then find cos θ​

Answer 1

ΔABC be a right angled at B

Let ∠ACB=θ

Given that, sin θ = 3/5

AB/AC = 3/5

Let AB = 3x

then AC = 5x

In right angled ΔABC,

By Pythagoras theorem,

We get

(5x)

2

=(3x)

2

+BC

2

BC

2

=(5x)

2

−(3x)

2

BC

2

=(2x)

2

BC=4x

(i) cos θ = Base/ Hypotenuse

= BC / AC

= 4x /5x

= 4/5

Answer 2

Answer:

cos θ =4/5

Step-by-step explanation:

ΔABC be a right angled at B

Let ∠ACB=θ

Given that, sin θ = 3/5

AB/AC = 3/5

Let AB = 3x

then AC = 5x

In right angled ΔABC,

By Pythagoras theorem,

We get

(5x)  2  =(3x)  2 +BC 2

BC  2 =(5x) 2 −(3x)  2

 BC  2  =(2x)  2

 BC=4x

(i) cos θ = Base/ Hypotenuse

= BC / AC

= 4x /5x

= 4/5

I hope it will help you