# Math Help - vectors

1. ## vectors

Find the smallest interior angle of the triangle ABC whose vertices are given:-

A = (3,1,-2) B = (3,0,-1) C = (5,2,-1)

I am not sure what to do here...i tried using the dot product but it didnt workout...any help??

2. Originally Posted by omibayne
Find the smallest interior angle of the triangle ABC whose vertices are given:-

A = (3,1,-2) B = (3,0,-1) C = (5,2,-1)

I am not sure what to do here...i tried using the dot product but it didnt workout...any help??
Find vector equations that represent the line segments that connect the three points. Then find the angle between them using the formula:

$\cos\vartheta=\frac{\bold u\cdot\bold v}{||\bold u|| ||\bold v||}\implies\vartheta=\cos^{-1}\left(\frac{\bold u\cdot\bold v}{||\bold u|| ||\bold v||}\right)$

--Chris

3. Originally Posted by Chris L T521
Find vector equations that represent the line segments that connect the three points. Then find the angle between them using the formula:

$\cos\vartheta=\frac{\bold u\cdot\bold v}{||\bold u|| ||\bold v||}\implies\vartheta=\cos^{-1}\left(\frac{\bold u\cdot\bold v}{||\bold u|| ||\bold v||}\right)$

--Chris
yeah i didnt find the equations for line segments....anyways thanks a lot for ur help