# Area of a triangle using vectors

1. Feb 18, 2015

### Calpalned

$1. The problem statement, all variables and given/known data Let P = (1,1,1), Q = (0, 3, 1) and R = (0, 1, 4). Find the area of triangle PQR 2. Relevant equations$ \frac {|PQ × PR|}{2} $= area (The crossproduct divided by two) 3. The attempt at a solution I lost my answer key, so I want to check if my final answer of$ \frac {\sqrt {13}}{2} $is right. Thanks everyone. If it isn't, I'll put up my work.$

2. Feb 18, 2015

### PhysyCola

Hey there Calpalned. I have worked the problem through, and I am not sure that your answer is correct. Are you sure you have evaluated the cross product correctly?

3. Feb 18, 2015

### Calpalned

I took the cross product of $<-1, 2, 0>$ and $<-1, 0,3>$ and I got $(0-0)-(-3-0)+(0--2)$ = $<0, 3, 2>$ Taking the magnitude, I get the answer in my first post.

4. Feb 18, 2015

### SammyS

Staff Emeritus
Not correct.

This should have vector components: $(0-0)-(-3-0)+(0--2)$ . What you have is a scalar.

The x-component of the result, $\ <0,\, 3,\, 2>\$ is incorrect.