Question

Write the complex number in the form a + bi.
3(cos 60° + i sin 60°)

Answer 1

3/2 + (3sqrt(3))/2 i

Explanation:

On the unit circle cosine and sine 60 degrees can be found in the first quadrant. With the correct measures. Once located, (1/2, sqrt(3)/2), multiply those numbers by 3. Don't forget to include i.

3(1/2 + sqrt(3)/2 * i)

= 3/2 + (3sqrt(3))/2 i

Answer 2

The complex number in the form of a + b i is 3/2 + i √3/2

Explanation:

* Lets revise the complex number in Cartesian form and polar form

- The complex number in the Cartesian form is a + bi

-The complex number in the polar form is r(cosФ + i sinФ)

* Lets revise how we can find one from the other

- r² = a² + b²

- tanФ = b/a

* Now lets solve the problem

∵ z = 3(cos 60° + i sin 60°)

∴ r = 3 and Ф = 60°

∵ cos 60° = 1/2

∵ sin 60 = √3/2

- Substitute these values in z

∴ z = 3(1/2 + i √3/2) ⇒ open the bracket

∴ z = 3/2 + i √3/2

* The complex number in the form of a + b i is 3/2 + i √3/2