Thomas Dean

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These are questions asked by Thomas Dean

When I was editing the head of the question (? instead of .), its body disappeared. Please, insert it again.

Regard,

Markiyan Hirnyk

Maple 15.

I have a set of equations I can solve manually, but, solve fails.

restart;
eq1 := tgtX[1] = 0;
eq2 := tgtY[2] - y[2]    = m[2]*(tgtX[2]-x[2]);
eq3 := tgtY[3] - y[3]    = m[3]*(tgtX[3]-x[3]);
eq4 := tgtY[4] - y[4]    = m[4]*(tgtX[4]-x[4]);
eq5 := tgtY[2] - tgtY[1] = vy*t[2];
eq6 := tgtY[3] - tgtY[1] = vy*t[3];
eq7 := tgtY[4] - tgtY[1] = vy*t[4];
eq8 := tgtX[2]           = vx*t[2];
eq9 := tgtX[3]           = vx*t[3];
eq10:= tgtX[4]           = vx*t[4];
#
# solve the equations
eqs  := {eq1,eq2,eq3,eq4,eq5,eq6,eq7,eq8,eq9,eq10};

solvx := solve(eq10,vx);
solvy := solve(eq7,vy);
sol1  := subs(vx=solvx,{eq8,eq9});
sol2  := subs(vy=solvy,{eq5,eq6});

soln  := subs(sol1,{eq2,eq3});

soln  := subs(tgtY[2]=solve(sol2[1],tgtY[2]),soln);
soln  := subs(tgtY[3]=solve(sol2[2],tgtY[3]),soln);
soln  := subs(tgtY[1]=solve(soln[1],tgtY[1]),soln[2]);
soln  := solve({eq4,soln},{tgtX[4],tgtY[4]});

# this returns empty solution
solve(eqs,{tgtX[4],tgtY[4]});

Any ideas?

Tom Dean

I have been here before...  My head is full of cotton, as usual.

 

f := proc (t) 2*t^3+9*t^2-60*t+1 end proc;
deq:=diff(f(t),t);
df := t->deq;  ## this is most likely one of my problems.
plot(df(t),t=-10..10);
isneg := x -> if is(df(x) < 0) then df(x) else 0 end if;  ## and, another??
plot(isneg(t),t=-10..10);
Plt1:=plot(isneg(t),t=-10..10);
plots:-display(Plt1);
isneg(0.12017234);

The if statement is not fully evauated.

I am missing something.  What?

Tom Dean

Maple 15

eq:=1/2*x^(1/2) + 1/13*x^(1/3) + 1/26*x^(45/37);
evalf(eq);

The exponents are still fractions.  I want to have floating point exponents.


0.5*x^0.500000 + 0.07692307692*x^0.333333 + 0.03846153846*x^1.216216216

How do I do this?

 

Tom Dean

The Maple11 loglog plot does a poor job in scaling and axis.  The plot works, but, compared to something like the Scilab bode plot, the scaling and axis presentation is poor.

Someone on another forum mentioned an application that improves this.  I searched and found nothing.

Is there an application that improves this?

tomdean

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