# Question:Four equations in four unknowns

## Question:Four equations in four unknowns

Maple

 >
 (1)
 >
 (2)
 > diff((2), y);
 (3)
 > diff((3), y);
 (4)
 >
 (5)
 > diff((5), x);
 (6)
 > diff((6), x);
 (7)
 >
 (8)
 > diff((8), x);
 (9)
 > diff((9), y);
 (10)
 (11)
 > -(1/16)*Pi^2*sin((1/4)*Pi*x)*(c__1*cosh((1/4)*Pi*y)+c__3*y*cosh((1/4)*Pi/y)+c__4*y*sinh((1/4)*Pi*y))=0;
 (12)
 > eval( (12), [x = 0]);
 (13)
 >
 (14)
 > eval( (14), [x = 20]);
 (15)
 >
 (16)
 > eval( (16), [y = 9]);
 (17)
 > evalf[5]( (17) );
 (18)
 >
 (19)
 > eval( (19), [y = -9]);
 (20)
 > evalf[5]( (20) );
 (21)
 >
 (22)
 > eval( (22), [y = 9]);
 (23)
 > evalf[5]( (23) );
 (24)
 >
 (25)
 > eval( (25), [y = -9]);
 (26)
 > evalf[5]( (26) );
 (27)
 > s:=solve({sin(.78540*x)*(362.25*c__1+0.84938e-3*c__3+4182.6*c__4) = 0,sin(.78540*x)*(362.25*c__1-0.84938e-3*c__3+4182.6*c__4) = -1.*sin(.25000*Pi*x),-.78540*cos(.78540*x)*(461.22*c__1+.99617*c__3+4738.2*c__4) = 0,-.78540*cos(.78540*x)*(-461.22*c__1+.99617*c__3-4738.2*c__4) = 0},{c1,c2,c3,c4});
 (28)
 >