Write a user$-$defined MATLAB function that determines the angle that forms by the intersection of two lines. For the function name and

arguments, use th$=$anglines $(A,B,C).$ The input arguments to the function are vectors with the coordinates of the points $A,B,$ and

$C,$ as shown in the figure, which can be two$-$ or three$-$dimensional. The output th is the angle in degrees. Use the function anglines

for determining the angle for the following cases:

$($a$)A(-5,-1,6),B(2\mathrm{.}5,1\mathrm{.}5,-3\mathrm{.}5),C(-2\mathrm{.}3,8,1)$

$($b$)A(-5\mathrm{.}5,0),B(3\mathrm{.}5,-6\mathrm{.}5),C(0,7)$