Straight Angle -- from Wolfram MathWorld

A straight angle is an angle equal to 180 degrees=pi radians. Two right angles make a straight angle, and two straight angles make a full angle.

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How to Calculate the Sides and Angles of Triangles Using

Regular N-gonal Right Antiprism: Application of HCR's Theory of

Prism -- from Wolfram MathWorld

Right Angle -- from Wolfram MathWorld

What Is Trigonometry?

Steinmetz Solid - From Wolfram MathWorld, PDF, Mathematics

Ask Ethan #6: The Center of the Universe

Fermat Points -- from Wolfram MathWorld

Great circle - Wikipedia

RF Inductance Calculator for Single‑Layer Helical Round‑Wire Coils

geometry - Calculating the height of a circular segment at all points provided only chord and arc lengths - Mathematics Stack Exchange

Vanishing Point -- from Wolfram MathWorld