area(y_):=area(y,x,0,1);

area(y_,x_):=area(y,x,0,1);
area(y_,a_,b_):=area(y,x,a,b);
area(y1_ and y2_,a_,b_):= abs(area(y1,x,a,b)-area(y2,x,a,b));
area(triangle(high_,length_)):=high*length/2;
area(sphere(r_)):=4*pi*r^2;
area(squres(length_)):=length^2;
area(circles(r_)):=pi*r*r;
area(ovals(rx_,ry_)):=pi*rx*ry;
area(x^2+y^2=r2_):=pi*r2;
area(a_*x^2+b_*y^2=r2_):=pi*sqrt(a*b)*r2;