Re: Angles between planes

Looks good to me, though I've been having trouble since my hari-kari.

Re: Angles between planes

Well, this is the wrong answer...unless the teacher is wrong. So I'm trying to figure out what's wrong here.

Re: Angles between planes

Quote:

Originally Posted by

**Bracketology** Well, this is the wrong answer...unless the teacher is wrong. So I'm trying to figure out what's wrong here.

Is your teacher's answer

That is the acute angle between the plane,

Re: Angles between planes

Yes. How do I find this angle?

Re: Angles between planes

Quote:

Originally Posted by

**Bracketology** Yes. How do I find this angle?

It usual in such a question to find the acute angle or maybe right angle.

Re: Angles between planes

Quote:

Originally Posted by

**Bracketology** Yes. How do I find this angle?

Pi - 1.89 (!)

Re: Angles between planes

When two planes (or two lines) intersect they make **four** angles but only two distinct angles- the "opposite" (vertical) angles are congruent. The two distinct angles between two planes add to radians. radians.

As to why that formula did not immediately give you the correct answer, note that <-1, 0, 1> is **also** normal to the first plane and if you had used that, you would have got . I.e., to get the smaller angle, use the absolute value.

Re: Angles between planes

Thanks for all the help guys!