Question

If sina =1/2 and a is an acute angle. Find the value of (3 cos a - 4cos3 a)

Answer 1

Step-by-step explanation:

Given:-

Sin a = 1/2 and a is an acute angle?

To find:-

Find the value of (3 Cos a - 4 Cos 3a)

Solution:-

Given that :

Sin a = 1/2

=> Sin a = Sin 30°

=>a = 30°

a is an acute angle

The value of an angle a = 30°

Now ,

The value of (3 Cos a - 4 Cos 3a)

=>3 Cos 30° - 4 Cos 3(30°)

=>3 Cos 30° - 4 Cos 90°

=>3 × (√3/2) - 4 × 0

=>3√3/2 - 0

=>3√3/2

Answer:-

The value of (3 Cos a - 4 Cos 3a) is 3√3/2

Check:-

• Sin 30° = 1/2

• Cos 30° = √3/2