## RWA Triangle Sum Theorem

### Topic

Spherical Geometry

### Vocabulary

- triangle sum theorem
- comparing angles and sides in triangles
- sphere
- Spherical Geometry

### Student Exploration

#### Do the angles in a triangle always add up to 180 degrees? How are the lengths of the sides of a triangle are controlled by the sizes of the angles in Spherical Geometry?

Watch the video below to learn more

http://www.mindset.co.za/learn/node/46354

### Extension Investigation

- Students can make a presentation like the one below http://www.youtube.com/watch?v=b7DmUymGR28&feature=related
- Virgo is one of the constellations of Zodaic. Three principal stars of the constellation form a triangle. If \begin{align*}m \angle S = 25\end{align*} and \begin{align*}m \angle P = 135\end{align*}, then find the \begin{align*}m \angle V\end{align*}. http://worksheets.tutorvista.com/angles-in-a-triangle-worksheet.html

#### Layering (optional)

How do we show that all of the angles the triangle add up to 180?

Watch these videos to see how