Find the angle subtended at the origin by the line segment whose end points are (0, 100) and (10, 0).
The distance $d$ between two points $\left(x_{1}, y_{1}\right)$ and $\left(x_{2}, y_{2}\right)$ is given by the formula
$d=\sqrt{\left(x_{1}-x_{2}\right)^{2}+\left(y_{1}-y_{2}\right)^{2}}$
In a right angled triangle the angle opposite the hypotenuse subtends an angle of
.
Here let the given points be A(0,100), B(10,0). Let the origin be denoted by O(0,0).
Let us find the distance between all the pairs of points
$A B=\sqrt{(0-10)^{2}+(100-0)^{2}}$
$=\sqrt{(-10)^{2}+(100)^{2}}$
$=\sqrt{100+10000}$
$A B=\sqrt{10100}$
$\begin{aligned} A O &=\sqrt{(0-0)^{2}+(100-0)^{2}} \\ &=\sqrt{(0)^{2}+(100)^{2}} \end{aligned}$
$=\sqrt{(0)^{2}+(100)^{2}}$
$A O=\sqrt{10000}$
$B O=\sqrt{(10-0)^{2}+(0-0)^{2}}$
$=\sqrt{(10)^{2}+(0)^{2}}$
$B O=\sqrt{100}$
Here we can see that $A B^{2}=A O^{2}+B O^{2}$.
So,
is a right angled triangle with ‘AB’ being the hypotenuse. So the angle opposite it has to be
. This angle is nothing but the angle subtended by the line segment ‘AB’ at the origin.
Hence the angle subtended at the origin by the given line segment is
.