Answer
The magnitude is 0
Work Step by Step
To solve this we use unit vectors of the direction to solve the equation.
$d1 $ is in the negative y direction $( -j) = ( 0, -1 )$
$d2$ is in the positive x direction $( i ) = ( 1, 0 )$
Tthe dot $( . )$ indicates dot product
$d1$ $.$ $(d2/4)$ = $(0$ $.$ $\frac{1}{4}) + ( -1$ $ .$ $0) = 0$
