# Hot Text™

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Captions can contain Hot Text™ links to object labels and values in your sketch. A Hot Text value changes dynamically as the value in the sketch changes, and a Hot Text label changes if the label of the object is changed. Use Hot Text to see an updated form of an equation or conjecture, to highlight or flash linked objects in a sketch, or to perform an action associated with an action button. |

| Use Hot Text to Write and Read Mathematics

As a mathematical writer, use Hot Text to:
• | Conveniently include proper mathematical notation for objects in your sketch.
• | Build explanations that refer to current names and values of objects in your sketch.
• | Document a construction, including links to hidden construction lines.
• | Share your writing so that others can read along, seeing the connections to your construction and performing actions on that construction.
• | Create equations or other mathematical expressions that incorporate values of sliders, parameters, or measurements.
• | Write an annotated proof of a mathematical theorem.
As a mathematical reader, you can use Hot Text in sketches created by others to:
• | See text and equations change in response to your manipulation of a sketch.
• | Use links to follow an argument or explanation described in a caption.
• | Press buttons within a caption to perform an action in the sketch.

| Insert Hot Text Labels and Values

While you’re editing a caption, insert Hot Text labels and values into the caption. The pointer shows a + sign when it’s over an object you can insert. You cannot create a Hot Text link to an object that depends on the caption in which you want to insert the Hot Text.
• | To insert a link to an object, click the object in the sketch. (The Default Link column of the table below lists the form of the link inserted for various objects.)
• | To insert a variant form of link to an object, hold the Shift key while you click the object, and choose a form from the pop-up menu that appears. (Available Variant Link forms are shown in the table below.)
• | To insert the label of an angle, create an angle marker by either pressing on one leg of the angle and dragging to the other leg, or by pressing on the vertex and dragging into the interior of the angle.
You can do this while you're editing the caption, without switching to the Marker tool. When you drag, the pointer appears as the Marker tool pointer. When you finish, Sketchpad creates the angle marker and inserts a Hot Text link into your caption.
Object | Default Link | Variant Link(s) (Requires Shift Key)
Point, Straight Object, Circle, Arc, Polygon or Other Interior, Locus, Function Plot, Parametric Plot, Iterated Image, Table | Label | None
Parameter | Value | Label, Value as Addend
Measurement | Value | Label, Value as Addend, Name
Calculation | Value | Label, Value as Addend, Calculation
Function | Full Equation | Label, Definition, Independent Variable, Dependent Variable
Angle Marker (drag in the sketch to create a marker and insert its name) | Name | Label
Action Button (pressing the link activates the button) | Label | None
Picture (a small icon of the picture appears in the caption) | Picture Icon | Description
Caption (hold the Shift key to insert a caption) | None | Full Text
Label: The label of the object Value: The value of a parameter, measurement, or calculation Value as Addend: The value preceded by a sign for addition or subtraction, depending on whether the value is positive or negative (This choice allows you to build nicely formatted expressions within a caption.) Name: The original name of a measurement or angle marker, showing what the object measures or marks (for instance, mABC for an angle measurement ) Calculation: The expression that defines the calculation (for instance, π·r2) Full Equation: The equation of the function as it's displayed in the sketch (for instance, f(x) = 2·x + 3) Definition: The definition of the function, without the label (For instance, 2·x + 3) Independent Variable: The label of the independent variable used in the function (for instance, x) Dependent Variable: The label of the dependent variable (for instance, f) Picture Icon: A small icon of the original picture. (To change the size of the icon, change its font size.) Description: The type and number of the object (for instance, Picture[1]) Full Text: The full text of the caption (An included caption doesn't flash like other Hot Text links, but is updated automatically.)

| Use a Caption Containing Hot Text

After you’ve created a caption containing Hot Text, you can interact with the caption.
• | Manipulate the sketch so that a value changes, and observe the changing value in the caption.
• | Change the label of an object in the sketch. The caption is updated automatically.
• | Highlight a linked sketch object by moving the pointer over the Hot Text link to the object.
Both the Hot Text and the object to which it links are highlighted (provided the object is visible), and Sketchpad displays an appropriate status message.
• | Flash a linked sketch object by pressing and holding the pointer on the Hot Text link to the object.
The object flashes even if it’s hidden.
• | Press a linked action button by pressing and releasing the pointer on the Hot Text link to the action button.
• | Click a Hot Text link from various dialog boxes, including the Calculator, Plot Points, Iteration, and Transform dialog boxes.
The linked object will be used as though you had clicked on it directly.

| Create a Mathematical Expression Containing Values

When you graph a function (like y = ax2 + bx + c) or calculate the value of an expression (like mx + b), you may want to create a caption that shows the function or expression with the numeric values inserted in place of the names of the parameters or measurements. For instance, if you've used two parameters (m = 2 and b = 3) to calculate the value of mx + b, you might want to create a caption that shows the expression as 2x + 3. This is easy as long as b is positive. While editing your caption, you can follow these steps:
1. | Click parameter m in the sketch to insert "2".
2. | Type "x + ".
3. | Click parameter b in the sketch to insert "3".
The result appears as "2x + 3." But if you change the value of b to make it negative (for instance, b = –1), the caption shows "2x + –1" instead of "2x – 1." To create an improved display, follow these steps instead:
1. | Click parameter m in the sketch to insert "2".
2. | Type "x ".
3. | Hold the Shift key while you click parameter b in the sketch. From the menu that appears, choose Value as addend.
The result of choosing Value as addend is a value that always includes the sign (either + or –). Depending on the value of b, the expression will appear correctly, as 2x + 3 or 2x – 1.