use cross product to get one side (n1)
n1= 2,0,0 x 1,1,7 = 0,-14, 2
use cross product to get another side (n2)
n2 = 0,2,0 x 1,1,7 = 14,0,-2
cos theta = (n1 x n2) / sqrt(sum of n1square) x sqrt(sum of n2 squares
-4 / sqrt(196+4) x sqrt(196+4)
-4/200
cos theta = - .02
theta = arccos (-.02) = 91.1
Find the angle, in degrees, between two adjacent sides of the pyramid.
P(2, 0, 0), Q(2, 2, 0), R(0, 2, 0), (base points)
S(1, 1, 7) (tip point)
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