Turn on function j(x) below (#17), and a point on this function as well (#18)
16
Expression 17: "j" left parenthesis, "x" , right parenthesis equals "x" squared plus 1jx=x2+1
17
Hidden Label: left parenthesis, "l" , "j" left parenthesis, "l" , right parenthesis , right parenthesisl,jl
Label
equals=
left parenthesis, negative 0.9 , 1.8 1 , right parenthesis−0.9,1.81
18
Now look at that point's reflection around y=x: turn on #20.
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Hidden Label: left parenthesis, "j" left parenthesis, "l" , right parenthesis , "l" , right parenthesisjl,l
Label
equals=
left parenthesis, 1.8 1 , negative 0.9 , right parenthesis1.81,−0.9
20
Drag the slider below to move the point on our function j, as well as its reflection. Optionally, turn on #23 as well, so better see the "connection" between these two points across y=x.
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Expression 22: "l" equals negative 0.9l=−0.9
negative 10−10
1010
22
Connecting line (function)
Hide this folder from students.
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As you animated these points, what shape do you see the reflected point drawing? Is this what you'd expect?
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Now turn on the #28 below to see the reflection of our original function.
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Expression 28: "k" left parenthesis, "y" , right parenthesis equals "j" left parenthesis, "y" , right parenthesisky=jy
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You can continue to animate the points above to see how these two relations are reflections of each other
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A last question: is our reflection around y=x a function? Answer this, and try to explain two ways in which you know this, in your notes.
30
Further explorations: Try different functions j(x), by editing #17. You can do this in real time while the reflection is displayed and the points are animating, to explore your results.