# Video tutorials (in construction)

### Example 1. (OK Geometry Simple)

Given is a triangle ABC with angle ∠C = 60 °.
E and F are the intersections (other than A and B) of the semicircle on AB with the sides BC and CA.

D is the centre of the semicircle on AB.
Observe the configuration.
• Import and observe a GeoGebra construction (video mp4).
• Inspect and observe construction files of various types.

### Example 2. (OK Geometry Plus)

The circle k touches inwardly two sides of the triangle ABC triangle and its circumcircle.
• Create the configuration in Sketch Editor. (video.mp4)
• Find a Euclidean construction of the circle k. (video mp4)
• Observe how the radius rk of the circle k is algebraically related to the quantities of triangle ABC. (video mp4)

### Example 3. (OK Geometry Plus)

Given is a triangle ABC. Let ka, kb, kc be the circles inscribed in the regions between incircle of ABC an the respective pairs of sidelines through A, B, C. Let k be the circle internally tangent to ka, kb and kc and let A', B' C'  be the points of contact of circles ka, kb, kc and k. It turns that the lines AA', BB' and CC' concur at a point P.

• Create the configuration in Sketch Editor. (video.mp4)
• Analyse the position of the point P in the reference triangle ABC.. (video mp4)
• Observe the trilinears of the point P in the reference triangle ABC.. (video mp4)