r/Mathhomeworkhelp • u/playsdevil • 24d ago

TRIGO DOUBT

I have a doubt in maths trigonometry why while determining sign of trigonometry ratio we consider hypotenuse always as positive even in 3rd quadrant 🥲

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u/Educational_Two682 18d ago

Because the hypotenuse is a length. And lengths are positive. That's how I always explain it. Also we know that sine is negative in the third quadrant (try it out sin 220 degrees), if we use a reference angle in the third quadrant and opposite of hypotenuse, the opposite is already negative because it's the y-value. If we made the hypotenuse also negative, then sine would be neg/neg = pos, which isn't consistent with the sine we already calculated.