Incircle Construction of a 9‑8‑7 Triangle

Overview

A step‑by‑step top‑down construction of the incircle of a triangle with side lengths 9 cm, 8 cm, and 7 cm. The animation mimics a clean mathematics notebook page: white background, thin black lines for straight edges, light blue arcs for compass constructions, and a final red incircle.

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Phases

#	Phase Name	Duration	Description
1	Setup	~2s	Draw horizontal segment $AB$ of length 9 cm, label $A$ left, $B$ right.
2	First Arc	~2s	Compass at $A$ with radius 8 cm draws a light‑blue arc above $AB$.
3	Second Arc & Point C	~2s	Compass at $B$ with radius 7 cm draws a second light‑blue arc; their intersection is marked as $C$.
4	Triangle	~2s	Connect $A$–$C$ and $B$–$C$ with thin black lines to form $\triangle ABC$.
5	Angle Bisector at A	~3s	Using the classic compass‑arc method, construct the bisector of $\angle A$ and draw the bisector line from $A$.
6	Angle Bisector at B	~3s	Repeat the compass‑arc method at $B$ to draw the bisector of $\angle B$.
7	Incenter	~2s	Intersection of the two bisectors is marked as $I$ and labeled “Incenter”.
8	Perpendicular to AB	~2s	From $I$ drop a perpendicular to side $AB$; mark foot $D$ and show a right‑angle marker.
9	Set Compass Width	~1s	Compass width is set to distance $ID$.
10	Draw Incircle	~2s	Draw a circle centered at $I$ with radius $ID$ in light blue.
11	Highlight Incircle	~2s	Change the circle’s stroke to red, label “Incircle of $\triangle ABC$”.
12	Outro	~2s	Fade out all construction lines except the final red incircle and triangle, hold briefly.

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Layout

┌─────────────────────────────────────────────┐
│                TITLE AREA                  │
├─────────────────────────────────────────────┤
│                     MAIN AREA               │
│                                             │
│   (centered notebook‑style diagram)         │
│                                             │
├─────────────────────────────────────────────┤
│                FOOTER AREA (optional)      │
└─────────────────────────────────────────────┘

Area Descriptions

Area	Content	Notes
Title	"Incircle Construction of a 9‑8‑7 Triangle" (small, fades in with phase 1)	Appears only at start, then fades out
Main	All geometric elements: segment $AB$, arcs, triangle, bisectors, incenter $I$, foot $D$, and final incircle.	Fixed camera, centered; elements appear sequentially per phase
Footer	Optional caption such as "Construction steps" or source note.	Can remain invisible if not needed

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Notes

• All straight lines are thin black strokes; compass arcs are light blue (opacity ~0.6) until the final circle, which becomes solid red.
• Labels (A, B, C, I, D) are small black text placed just offset from the points; they appear together with the point they label.
• Right‑angle marker is a small square glyph at $D$.
• Camera remains fixed directly above; no zoom or pan.
• Transitions between phases are simple fades or draws; each construction step is deliberately paced to allow a viewer to follow the logic.
• Total runtime ≈ 25 seconds, well within the 30‑second guideline.