so i have to determine the obtuse angle between the diagonals in the following diagram:(adsbygoogle = window.adsbygoogle || []).push({});

http://img95.imageshack.us/img95/6112/obtuse9hg.jpg [Broken]

this is what i have so far:

let's call the intersection of the diagonals O

so to find the obtuse angle, we can apply dot product (OW • OZ)

|OW| = 1/2 |YW|

= sqrt(61)/2

|OZ| = 1/2 |XZ|

= 3sqrt(24)/2

but if cos (theta) = (OW • OZ)/ (|OW||OZ|)

i don't have the numerator portion which is usually found with coordinates. so what do i do now?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Dot product

**Physics Forums | Science Articles, Homework Help, Discussion**