# ANSWER[row] as synonymous of \$row cmd

Jaime shared this idea 6 years ago
Declined

Idea, please GG TEAM add the ANSWER[row] command as synonymous with the \$row command to make the instruction sequences in the CAS view more understandable for the students.

The following sequence of statements, show step by step the solution of a simple list of equations.

with \$ cmd

1. { y = x^2, y = 2*x + 3 } { y = x^2, y = 2*x + 3 }
2. Substitute[Element[\$1,2],Element[\$1,1]] x^(2) = (2 * x) + 3
3. \$2 - (2x + 3) x^(2) - (2 * x) - 3 = 0
4. Factor[LeftSide[\$3]] ((x - 3) * (x + 1))
5. {Element[\$4,1] = 0, Element[\$4,2] = 0} {x - 3 = 0, x + 1 = 0}
6. {Element[\$5,1] + 3, Element[\$5,2] - 1} {x = 3, x = (-1)}
7. Substitute[Element[\$1,1],Element[\$6,1]] y=9
8. Substitute[Element[\$1,2],Element[\$6,1]] y=9
9. Substitute[Element[\$1,1],{\$8, Element[\$6,1]}] 9=9
10. LeftSide[\$9] ≟ RightSide[\$9] -> true

1. { y = x^2, y = 2*x + 3 } { y = x^2, y = 2*x + 3 }
3. answer[2] - (2x + 3) x^(2) - (2 * x) - 3 = 0
4. Factor[LeftSide[answer[3]]] ((x - 3) * (x + 1))
5. {Element[answer[4],1] = 0, Element[answer[4],2] = 0} {x - 3 = 0, x + 1 = 0}
6. {Element[answer[5],1] + 3, Element[answer[5],2] - 1} {x = 3, x = (-1)}

Syntax in XCAS

1. [ y = x^2, y = 2*x + 3 ] returns [ y = x^2, y = 2*x + 3 ]
2. subst((ans(-1)(2)),ans(-1)(1)) returns x^2=(2*x+3)
3. ans(-1) - (2*x + 3) returns x^2-2*x-3=0
4. factor(ans(-1)) returns (x-3)*(x+1)=0
5. [ part(left(ans(-1)),1)=0, part(left(ans(-1)),2)=0 ] returns [x-3=0,x+1=0]
6. ans(-1)(1)+3, ans(-1)(2)-1 ] returns [x=3,x=-1]
7. subst(y=x^2,ans(-1)(1)) returns y=9
8. subst(y=2*x + 3,ans(-2)(1)) returns y=9
9. subst(y=2*x + 3,[ans(-3)(1),ans(-1)]) returns 9=9
10. evalb(ans(-1)) returns 1 (true)

1

Why do you think that's clearer?

1

Now I'm starting with GG and in my presentations in the classroom, students tell me that the \$ symbol is not very natural in functional algebraic syntax

1

OK, see if they get used to it soon :)

1

We (Teacher, students) really do not like the \$ command as a call to a position in a history stack., it's not natural notation about calculators (ti-nspire [cx cas] family , hp-prime cas, etc. [Portable device and computer software])

I'm going to create several CAS type scripts that will soon share them, but I insist that there should be a synonym for the \$ command, I think that there is no need to make any big changes in the interpretation of expressions. But the idea is not to use CAS proprietary \$\$ [MATLAB (SYM TOOLBOX), MATHEMATICA, etc] software, to switch to free software as the GG calculator, xCAS

As an extra suggestion, accept a second parameter to compact the sentence

I propose that the ans command can accept an optional second argument, extract the x element from the previous list of objects

current

1. { y = x^2, y = 2*x + 3 } { y = x^2, y = 2*x + 3 }
2. Substitute[Element[\$1,2],Element[\$1,1]] → x^(2) = (2 * x) + 3

In a future GG update (As a Optional notation)

1. { y = x^2, y = 2*x + 3 } { y = x^2, y = 2*x + 3 }
2. Substitute[ answer[1,2], [answer[1,2] ] x^(2) = (2 * x) + 3

Thanks