Trigonometric EquationHard
Question
The resultant of two forces P N and 3 N is a force of 7 N. If the direction of 3 N force were reversed, the resultant would be √19 N. The value of P is
Options
A.5 N
B.6 N
C.3 N
D.4 N
Solution

72 = P2 + 32 + 2 × 3 × P cosθ .... (1)
(√19)2 = P2 + (-3)2 + 2 × (-3) × P cos θ ....(2)
adding we get
68 = 2P2 + 18 ⇒ P = 5.
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