Trigonometry

If 2 triangles are congruent then the 2 triangles are similar.
An isosceles triangle has two sides of equal length.
The 3 angles of any triangle always add up to 180 degrees.

Pythagoras Theorem

This applies to all right angled triangles
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SOH CAH TOA

Sine is Opposite over Hypotenuse
Cosine is Adjacent over Hypotenuse
Tangent is Opposite over Adjacent