Question

two vectors of magnitude 10N and 15N are acting at a point the magnitude of their resultant is 20N the angle between them will be

Answer 1

$resultant = \sqrt{ {x}^{2} + {y}^{2} + 2xy \cos(a) }$
x=10N and y=15N . a is the angle between them .
20=√10^2 +15^2 +2(10)(15)cos(a) => on squaring On both sides, we get 400=100+225+300cos(a)=> 400-325=75=300cos(a) => cos(a)= 1/4 => a=cos inverse (1/4).

Answer 2

Answer:

Fx=10

Fy=15

F=20

according to law of cosine

F= (Fx²+Fy²+2Fx.Fycos@)½

20=(10²+15²+2(10)(15)cos@)½

20=(100+225+300cos@)½

20=(625cos@)½

squaring both sides

20²={(625cos@)½}²

400=625cos@

400÷625=cos@

0.64=cos@

cos‐¹(0.64)=@

50.2=@

Explanation:

here @ is used for angle