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find the sin angle between two 2d vectors


Oct 19, 2017
Tomorrow is my math test and I'm going over the study guide:

I have vector U=<1, 3> and vector V=<5, 2>

It says let theta be the missing angle between the two vectors. What is the cos(theta) and sin(theta)?

I already know how to find the missing angle for cos(theta) but we never covered how to find the missing angle for sin(theta). It was never in our homework and it's not in my notes but apparently it could be on the test.

So if someone could give me the formula and then show a step by step on how to do this it would be most appreciated.


Staff member
Feb 24, 2012
Once you know \(\cos(\theta)\), then given \(0\le\theta\le\pi\), we may use a Pythagorean identity:

\(\displaystyle \sin(\theta)=\sqrt{1-\cos^2(\theta)}\)