If the point (α, (7 √ 3)/3) lies on the curve traced by the mid-points of the line segments of the lines x cos θ+y sin θ=7, θ ∈(0, (π)/2) between the…

If the point $\displaystyle \left(\alpha, \frac{7 \sqrt{3}}{3}\right)$ lies on the curve traced by the mid-points of the line segments of the lines $\displaystyle x \cos \theta+y \sin \theta=7, \theta \in\left(0, \frac{\pi}{2}\right)$ between the co-ordinates axes, then $\displaystyle \alpha$ is equal to