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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)???

 Jul 3, 2016

Best Answer 

 #1
avatar+9665 
+10

\(cos30 = \dfrac{adjacent \space side}{20}\)

\(adjacent \space side = 20 cos30 = 10\sqrt3\)

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

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

 

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

 Jul 3, 2016
 #1
avatar+9665 
+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

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