Entering TwoDimensional Input
When Mathematica reads the text x^y, it interprets it as x raised to the power y.
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In a notebook, you can also give the twodimensional input x^{y} directly. Mathematica again interprets this as a power.
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One way to enter a twodimensional form such as
x^{y} into a
Mathematica notebook is to paste this form into the notebook by clicking the appropriate button in the palette.
Here is a palette for entering some common twodimensional notations. 
There are also several ways to enter twodimensional forms directly from the keyboard.
x Ctrl+^ y Ctrl+Space  use control keys that exist on most keyboards 
x Ctrl+6 y Ctrl+Space  use control keys that should exist on all keyboards 
Ways to enter a superscript directly from the keyboard.
You type
Ctrl+^ by holding down the
Control key, then pressing the
^ key. As soon as you do this, your cursor will jump to a superscript position. You can then type anything you want and it will appear in that position.
When you have finished, press
Ctrl+Space to move back down from the superscript position. You type
Ctrl+Space by holding down the
Control key, then pressing the
Space bar.
This sequence of keystrokes enters x^{y}.
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Here the whole expression y+z is in the superscript.
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Pressing Ctrl+Space takes you down from the superscript.
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You can remember the fact that
Ctrl+^ gives you a superscript by thinking of
Ctrl+^ as just a more immediate form of
^. When you type
x^y,
Mathematica will leave this onedimensional form unchanged until you explicitly process it. But if you type
x Ctrl+^ y then
Mathematica will immediately give you a superscript.
On a standard Englishlanguage keyboard, the character
^ appears as the shifted version of
6.
Mathematica therefore accepts
Ctrl+6 as an alternative to
Ctrl+^. Note that if you are using something other than a standard Englishlanguage keyboard,
Mathematica will almost always accept
Ctrl+6 but may not accept
Ctrl+^.
x Ctrl+_ y Ctrl+Space  use control keys that exist on most keyboards 
x Ctrl+ y Ctrl+Space  use control keys that should exist on all keyboards 
Ways to enter a subscript directly from the keyboard.
Subscripts in
Mathematica work very much like superscripts. However, whereas
Mathematica automatically interprets
x^{y} as
x raised to the power
y, it has no similar interpretation for
x_{y}. Instead, it just treats
x_{y} as a purely symbolic object.
This enters y as a subscript.
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Here is the usual onedimensional Mathematica input that gives the same output expression.
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x Ctrl+/ y Ctrl+Space  use control keys 
How to enter a builtup fraction directly from the keyboard.
This enters the builtup fraction .
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Here the whole y+z goes into the denominator.
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But pressing Ctrl+Space takes you out of the denominator, so the +z does not appear in the denominator.
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Mathematica automatically interprets a builtup fraction as a division.
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Ctrl+@ x Ctrl+Space  use control keys that exist on most keyboards 
Ctrl+2 x Ctrl+Space  use control keys that should exist on all keyboards 
Ways to enter a square root directly from the keyboard.
Ctrl+Space takes you out of the square root.
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Here is the usual onedimensional Mathematica input that gives the same output expression.
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Ctrl+^ or Ctrl+6  go to the superscript position 
Ctrl+_ or Ctrl+  go to the subscript position 
Ctrl+@ or Ctrl+2  go into a square root 
Ctrl+% or Ctrl+5  go from subscript to superscript or vice versa, or to the exponent position in a root 
Ctrl+/  go to the denominator for a fraction 
Ctrl+Space  return from a special position 
Special input forms based on control characters. The second forms given should work on any keyboard.
This puts both a subscript and a superscript on x.
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Here is another way to enter the same expression.
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The same procedure can be used to enter a definite integral.
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In addition to subscripts and superscripts,
Mathematica also supports the notion of underscripts and overscripts—elements that go directly underneath or above. Among other things, you can use underscripts and overscripts to enter the limits of sums and products.
x Ctrl+Plus y Ctrl+Space or x Ctrl+= y Ctrl+Space 
 create an underscript 
x Ctrl+& y Ctrl+Space or x Ctrl+7 y Ctrl+Space 
 create an overscript 
Creating underscripts and overscripts.
Here is a way to enter a summation.
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