https://www.hackerrank.com/challenges/class-2-find-the-torsional-angle
You are given four points A, B, C and D in a 3-dimensional Cartesian coordinate system. You are required to print the angle between the plane made by the points A, B, C and B, C, D in degrees(not radians). Let the angle be PHI.
Cos(PHI) = (X.Y)/|X||Y| where X = AB x BC and Y = BC x CD.
Here, X.Y means the dot product of X and Y, and AB x BC means the cross product of vectors AB and BC. Also, AB = B - A.
Input Format
One line of input containing the space separated floating number values of the X, Y and Z coordinates of a point.
Output Format
Output the angle correct up to two decimal places.
Sample Input 0
0 4 5
1 7 6
0 5 9
1 7 2
Sample Output 0
8.19