Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 5 - No. 20)
When using the Law of Cosines, if the included angle is 90 degrees, what does the formula simplify to?
a^2 + b^2 = c^2
a^2 + c^2 = b^2
b^2 + c^2 = a^2
The Law of Cosines cannot be applied
Explication
If angle A = 90°, cos(90) = 0, and the formula becomes the Pythagorean theorem.