Matlab,求不等式中两个变量差的范围

这个方程太复杂了,我的笔记本全速跑了好几分钟也没跑出来,你自己试试吧,可以是我算法不太好.代码如下
syms f d
D=maple('solve({-1/8*cos(3*f-3*d)+1/16*f^4+1/16*d^4+1/2*f^2*cos(f-d)-f*d*cos(f-d)+1/2*d^2*cos(f-d)+1/16*cos(2*f-2*d)*f^2+1/16*cos(2*f-2*d)*d^2+7/32*cos(2*f-2*d)+1/8*cos(f-d)+1/128*cos(-4*d+4*f)-1/2*f*sin(2*f-2*d)-d*sin(f-d)+1/2*d*sin(2*f-2*d)-9/16*f^2-9/16*d^2-1/4*f^3*d+3/8*f^2*d^2-1/4*f*d^3+f*sin(f-d)+9/8*f*d-1/8*cos(2*f-2*d)*f*d-29/128