if vectors P Q R have magnitude 5 12 13 units and P + Q vector is equal to R vector then the angle between q and R is
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Explanation:
P&Q are two vectors
R is resultant of following vectors.
it's right angled triangle....
P = 5 units
Q = 12 units
R = 13 units
find the angle between Q & R
according to formula........
R = √ A^2 + B^2 + 2AB cos theta
13 = √ 25+ 144 + 120 cos theta
squaring on both sides
169 = 169+120 cos theta
169 = 299 cos theta
0.5 = cos theta
1/2 = cos theta
but cos 60 = 1/2
therefore......
theta = 60°
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