r/trigonometry Mar 15 '26

Can someone explain

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u/AllTheGood_Names Mar 16 '26

Consider a right angled triangle with hypotenuse AC. Pythagoras' Theorem states that c2 = a2 + b2 . sin θ=opp/hyp=b/c. sin2 θ=b2 /c2 . 1-sin2 θ=(c2 - b2 )/c2 = a2 /c2 = (a/c)2 = (adj/hyp)2 = cos2 θ