爱华网diff
Differentiate symbolic expression_r_r求符号表达式的微分Syntax
diff(expr)diff(expr, v)
diff(expr, sym('v'))
diff(expr, n)
diff(expr, v, n)
diff(expr, n,v)
Description
diff(expr) differentiates a symbolicexpression_r_r expr wi th respect toits free variable as determined by symvar.diff(expr,v) and diff(expr, sym('v')) differentiateexpr with respect tov.diff(expr,n) differentiates expr ntimes. n is a positiveinteger.diff(expr, v,n) and diff(expr, n, v)differentiate expr with respect tov n times.diff(expr) 求一个符号表达式expr相对于由symvar确定的自由变量的微分。Examples
Differentiate the following single-variable expression_r_r onetime:syms x;diff(sin(x^2))The result is
ans =2*x*cos(x^2)
diff(t^6,6)The result is
ans =720
diff(sin(x*t^2), t)The result is
ans =2*t*x*cos(t^2*x)
综合应用
给定函数f(x)=cosx/(x3+7x+2)的一阶导数，并将每个点上的值与原函数的值通过matlab函数绘制出来.subs用法见http://blog.sina.com.cn/s/blog_4b94ff130100gdk9.html- 一阶导数syms x;
f=cos(x)/(x^3+7*x+2);
f1d=diff(f,x)pretty(f1d) - 绘制原函数以及求导后函数曲线
x1=0:0.001:5;
y=subs(f,x,x1);
y1d=subs(f1d,x,x1);
plot(x1,y,x1,y1d,':')
