If angle between a vector and b vector is 30° then find (b*a).a
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Vector A , B and A+B have the same magnitude a= b
A+B have the same direction and magnitude as the the diagonal of a parallelogram formed by A and B, ( see figure)
mag(A+B)= a^2+b^2+2.a.b.cos(alpha)
where alpha is the angle formed by A and B
replace mag(A+B)= mag(A)=mag(b)= a we will get
cos(alpha)= -1/2
so alpha= 120 degrees
A+B have the same direction and magnitude as the the diagonal of a parallelogram formed by A and B, ( see figure)
mag(A+B)= a^2+b^2+2.a.b.cos(alpha)
where alpha is the angle formed by A and B
replace mag(A+B)= mag(A)=mag(b)= a we will get
cos(alpha)= -1/2
so alpha= 120 degrees
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