Flowchart Proofs

Part of the Congruence & Proof section of Coddy's Geometry journey. Lesson 31 of 60.

A proof does not have to be a table. A flowchart proof writes each statement in a box, with its reason under it, and draws arrows from the facts a step uses to the step. The arrows do the job of the citations.

$Triangles WXY and WXZ sharing WX, with XY and XZ ticked and the angles at X marked$

For this figure, three boxes sit side by side: XY = XZ (Given), ∠WXY = ∠WXZ (Given) and WX = WX (Reflexive property). Arrows from all three point to △WXY ≅ △WXZ (SAS), and one arrow from there points to WY = WZ (CPCTC). It is the same proof as a table, laid out so you can see which facts feed which step.

Challenge

In quadrilateral RSTU the ticks show RS = RU, and the diagonal RT splits the angle at R into two angles marked equal. Prove that ∠RST = ∠RUT as a flowchart, then press Check.

Each box is a statement with its reason. While you write a box, tap the numbers of the boxes it uses, and the arrows appear.

Try it yourself

$Write the proof$