NCERT Class XI Mathematics - Complex Numbers and Quadratic Equations - Solutions

© examsnet.com
Question : 21
Total: 52
3 + i
Solution:  
We have , 3 + i
Let 3 = r cosθ …(i) and 1 = r sinθ …(ii)
Squaring and adding (i) and (ii), we get
r2(cos2θ+sin2θ) = 3 + 1 ⇒ r2 = 4 ⇒ r = 2
Substituting the value of r in (i) and (ii), we get 2 cos θ = 3 , 2 sin θ = 1
⇒ cos θ =
3
2
, sin θ =
1
2
⇒ cos θ = cos
π
6
, isn θ = sin
π
6

Here , cos θ and sin θ both are positive.
∴ θ lies in first quadrant. ∴ θ =
π
6

∴ The required polar form is z = 2 (cos
π
6
+isin
π
6
)
© examsnet.com
Go to Question: