Given that the magnitude of each of the two vectors $\overset{\rightarrow}{a}$ and $\overset{\rightarrow}{b}$ have same magnitude. ⇒ $\left|\overset{\rightarrow}{a}\right|$ = $\left|\overset{\rightarrow}{b}\right|$ ... (i) the angle between $\overset{\rightarrow}{a}$ and $\overset{\rightarrow}{b}$ is 60° ⇒ θ = 60° and $\overset{\rightarrow}{a}$ . $\overset{\rightarrow}{b}$ = $\frac{3}{2}$ ... (iii) Since, $\overset{\rightarrow}{a}$ . $\overset{\rightarrow}{b}$ = $\left|\overset{\rightarrow}{a}\right|$ $\left|\overset{\rightarrow}{b}\right|$ cos θ ⇒ $\left|\overset{\rightarrow}{a}\right|$ $\left|\overset{\rightarrow}{a}\right|$ cos 60° = $\frac{9}{2}$ From (i),(ii) and (iii) ⇒ $\left|\overset{\rightarrow}{a}\right|^2$ × $\frac{1}{2}$ = $\frac{9}{2}$ ⇒ $\left|\overset{\rightarrow}{a}\right|^2$ = 9 ⇒ $\left|\overset{\rightarrow}{a}\right|$ = 3 ⇒ $\left|\overset{\rightarrow}{a}\right|$ = $\left|\overset{\rightarrow}{b}\right|$ = 3 ... From (i)