physics
posted by koks on .
find the magnitude of vector by scalar and vector A= ? + 4j +4k B= ? + 2j + 3k if the angle between them 15 degrees.

There is some algebra to this..
AdotB=MagA*MagB*costheta
ab+8+12=sqrt[(a^2+14+16)(b^2+4+9)]*cosTheta
which cant be solved, unless a,b are equal where a and b are the i components of each vector. Assuming them the same,
a^2+20=sqrt[(a^2+30)(a^2+13)] * cos15
now square both sides, find a
Vectors are A=ai+4j+4k and B=ai+2J+3k)