Basic Trigonometry HELP????

Question

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How do you find the opposite angle in a triangle when you only know the cosine angle degrees (30 degrees) and the hypotenuse length (20m)???

Guest Jul 3, 2016

+9676

+10

Best Answer

$cos30 = \dfrac{adjacent \space side}{20}$

$adjacent \space side = 20 cos30 = 10\sqrt3$

$opposite \space side=\sqrt{20^2-(10\sqrt3)^2}=\sqrt{100}=10$

$atan(\dfrac{10\sqrt3}{10})= atan(\sqrt3)=60 \space degrees$

Wait, if that is for right-angled triangles why I don't just 90 - 30 ...... never mind, at least I got the answer XD

MaxWong Jul 3, 2016

MaxWong · Answer 1 · 2016-07-03T07:07:58

$cos30 = \dfrac{adjacent \space side}{20}$

$adjacent \space side = 20 cos30 = 10\sqrt3$

$opposite \space side=\sqrt{20^2-(10\sqrt3)^2}=\sqrt{100}=10$

$atan(\dfrac{10\sqrt3}{10})= atan(\sqrt3)=60 \space degrees$

Wait, if that is for right-angled triangles why I don't just 90 - 30 ...... never mind, at least I got the answer XD