\[T\sum [\sin(x^2+y^2)=t]\]Trigonometric function “ sine or cosine ” expresses periodicity. Quadratic expression "\(\left(x^2+y^2\right)\)" shows circular shape.
Expression factor "\(t\)" associates these characteristics.
T-expression , Math Art skill is investigated by TAKADA Tashiyoshi in 2000.
Fig.6 T-expression is designed;
" \(x\sin t + y\cos t\) " called rotation structure makes rotate a shape with a center of the origin either clockwise or counterclockwise.
Fig.9 \(x\sin t + y\cos t =x^2+y^2\) ;90 circles make yellow round cookie.
Fig.10 \(x\sin t + y\cos t = x^2+y^2-3\) ;90 circles make magenta doughnut.