Key to mAtlaB Exercise 7 School of Mathematical Sciences Xiamen University h http:/edjpkc.xmu.ed >>clear; syms x y,g(x3 y-5* y)(2 x2+7);g xy=diff(difi(.x),y) compose(g xy, 1) 3/81 >>clear; syms gg=(x3*y-5*y)(2x2+7) >>gy=diff(g,y) gy- (x^3-5)(2*x^2+7) > subs(g y, [x,[1 2D) 4/9 >> clear; syms x f, fsin(x)*sin(2*x)*sin(3*x); > diff(f,5 1696cos(x)*sin(2*x)*sin(3*x)+2192*sin(x)*cos(2*x)*sin(3*)+2208*sin(x)*sin(2*x)*cos(3 x)-1680*cos(x)*cos(2*x)*cos(3*) 7 >>A=[15,8-2,6,3]B=(-1)*difA) >>A=[1,5,8-2,6,3];C= difI(A2 8. >>clear; syms x y; y=1/(x+1); >> int(y) > clear; syms y; y=1/(x+1); nt(y0,1) log(2) > clear; syms xt y, y=1/(x+l) > int(y, 0, t) ans logit+ Ex7-4Key to MATLAB Exercise 7  School of Mathematical Sciences Xiamen University  http://gdjpkc.xmu.edu.cn  Key to Ex7­4  >> clear; syms x y g; g=(x^3*y­5*y)/(2*x^2+7); g_xy=diff(diff(g,x),y) >> compose(g_xy,1) ans =  43/81  3) >> clear; syms x y g; g=(x^3*y­5*y)/(2*x^2+7);  >> g_y=diff(g,y) g_y =  (x^3­5)/(2*x^2+7) >> subs(g_y, [x y], [1 2]) ans =  ­4/9  4) >> clear; syms x f; f=sin(x)*sin(2*x)*sin(3*x);  >> diff(f,5) ans =  1696*cos(x)*sin(2*x)*sin(3*x)+2192*sin(x)*cos(2*x)*sin(3*x)+2208*sin(x)*sin(2*x)*cos(3  *x)­1680*cos(x)*cos(2*x)*cos(3*x) 7.  1) >> A=[1,5,8,­2,6,3]; B=(­1)*diff(A) B =  ­4  ­3  10  ­8  3  2) >> A=[1,5,8,­2,6,3]; C=diff(A,2) C =  ­1  ­13  18  ­11  8.  1) >> clear; syms x y; y=1/(x+1);  >> int(y) ans =  log(x+1) 2) >> clear; syms x y; y=1/(x+1);  >> int(y,0,1) ans =  log(2) 3) >> clear; syms x t y; y=1/(x+1);  >> int(y,0,t)  ans =  log(t+1)  4)