Question 1193368
Use the Cosine Law to find r.
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r^2 = p^2 + q^2 -2*p*q*cos(50)
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But, r is not the resultant force.
Complete the parallelogram by adding the 2 sides parallel to p and q
Call the resultant force f.  f is the long diagonal.
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f^2 = p^2 + q^2 -2*p*q*cos(130)
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Change the values of p and q, calculate f again.