Question

Angle between two vectors of magnitudes 12 and 18 units, when their resultant is 24 units is

(a) 82°31'

(b) 63°51'

(c) 89°16'

(d) 75°52'

Answer 1

Correct option (d) 75°52'

Explanation :

Given : Magnitude of first vector (A) = 12

Magnitude of second vector (B) = 18 and resultant of the given vectors (R) = 24. Resultant vector

Answer 2

Let the angle be A

So

24^2=12^2+18^2+2×12×18cosA

=>cosA=(576-144-324)/(24×18)=0.25

=>A=cos^-1(0.25)=75.52°