Partially rotated coordinate systems

[Bassalisk]

Hello,

I am trying to understand this partially rotated coordinate systems.

I do not understand how does x'=xcos(theta)+ysin(theta) and y'=ycos(theta)-xsin(theta)

I am probably stuck at silly answer but i need this to understand deriving of formulas for special relativity.

Thanks

 

[Studiot]

If you want a proof look at page 2 here

http://www.stewartcalculus.com/data/CALCULUS Early Transcendentals/upfiles/RotationofAxes.pdf

 

[Bassalisk]

If you want a proof look at page 2 here

http://www.stewartcalculus.com/data/CALCULUS Early Transcendentals/upfiles/RotationofAxes.pdf

Thanks