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Derived formula 1:
a • b = ax + bx * is * by
= (|a|*sinθ1) * (|b| * sinθ2) + (|a| * cosθ1) * (|b| * cosθ2)
= |a||b|(sinθ1*sinθ2 + cosθ1*cosθ2)
=|a||b|(cos(θ1-θ2))
= |a||b|cosθ
Derived formula 2:
Geometric meaning: is multiplied by the length of an edge to another edge of the other side of the projection
Cross product:
