complex numbers (1 Viewer)

[Pace_T]

hi i have a question from uni but i think it's in 4 unit
here it is;
find the complex number (in cartesian form) obtained by rotating 6-7i anticlockwise about the origin through an angle 3pi/4
thanks.

 

[243_robbo]

convert to polar, add the desired number of pi radians then convert back

 

[Pace_T]

i tried doing that
but i cant get the sum done nicely
tan^-1 (-7/6) + 3pi/4 doesnt go well