Angle Between Planes: Calculating the Angle Between Two 3D Planes

[phospho]

find the angle between planes:

2x + y + 3z = 5
2x + 3y + z = 7

could someone double check this for me, I got 135.58 while the book got 44.4

thanks :s

 

[voko]

135.6 and 44.4 add up to 180. Interesting, eh?

 

[phospho]

135.6 and 44.4 add up to 180. Interesting, eh?

yes I noticed that...

 

[phospho]

is one the obtuse angle between the planes and the other the acute?

 

[voko]

Yep.