Question

A million years ago, an alien species built a vertical tower on a horizontal plane. When they returned they discovered that the ground had tilted so that measurements of 3 points on the ground gave coordinates of (0, 0, 0), (1, 2, 0), and (0, 2, 1). By what angle does the tower now deviate from the vertical?

Answer 1

Answer:

$\theta=cos^{-1}(\frac{2}{3})$

Step-by-step explanation:

We are given that measurements of three points on the ground gave coordinates of (0,0,0),(1,2,0) and (0,2,1)

We have to find the angle by which the tower now deviate from the vertical

We find cross product of <1,2,0> and <0,2,1>

$\times =\begin{vmatrix}i&j&k\\1&2&0\\0&2&1\end{vmatrix}$

$\times =2\hat{i}-\hat{j}+2\hat{k}$

Now, we are finding the angle between  $\times$and vertical vector <0,0,1>

Angle between two vectors formula

$cos\theta=\frac{a.b}{\mid a\mid\cdot\mid b\mid }$

Now, using this formula

$cos\theta=\frac{2}{1\cdot 3}=\frac{2}{3}$

$\theta=cos^{-1}(\frac{2}{3})$

Hence, the tower deviate from the vertical by the angle $\theta=cos^{-1}(\frac{2}{3})$