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The area of a regular pentagon looks about twice as a big as the pentangle star drawn within it. Is it?

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No Right Angle Here

Prove that the internal angle bisectors of a triangle will never be perpendicular to each other.

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A Sameness Surely

Triangle ABC has a right angle at C. ACRS and CBPQ are squares. ST and PU are perpendicular to AB produced. Show that ST + PU = AB


Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2
The green triangle is an isosceles triangle while the blue triangle is an equilateral triangle.

An isoceles triangle circumscribing and equilateral triangle with angles between the vertices of the equilateral triangle and isosceles triangle of a, b and c
Find $a$ in terms of $b$ and $c$.

What can you say about the triangles if $a = b = c$?