1.

The resultant of three vectors 1, 2 and 3 units whose directions are those of the sides of an equilateral triangle is :

Answer»

at an angle of 30° with the first vector
at an angle of 15° with the first vector
at an angle of 100° with the first vector
at an angle of 150° with the first vector

Solution :`R_(X)=1+2cos120^@+3cos240^@`
or `R_(x)=1+2(-1/2)+3(-1/2)=-3/2`

`R_(y)=2sin120^@+3sin240^@``=-sqrt(3)/2`
`tantheta=R_(y)/R_(x)=(-sqrt(3)/2)/(-3/2)=sqrt(3)/3=1/sqrt(3)`
`theta=tan^(-1)(1/sqrt(3))=30^@`


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