# typo

1. ### Typo?

Heya, Looking at an introduction to vectors. In my textbook it gives the example question: "A particle of mass 0.1kg is held at rest on a rough plane inclined at 20Â° to the horizontal by a friction force, F, acting up the plane. Find the magnitude of F and the normal reaction." The given...
2. ### Typo?

Beer soaked speculation follows. A college student emailed me the following right triangle problem: An airplane starts from a station and rises at an angle of 10Â° with the horizontal. By how many feet will it clear a vertical wall 110 ft. high and 900 ft. from the station? Assume that tan...
3. ### Is there a typo in the problem about factorials?

Here is the question with a possible error. (ex) When solving \frac{3n(n-2)!}{(n-3)!}=105 algebraically for n, which answer is eliminated because of the restrictions on factorials? (a) -5 (b) -4 (c) -3 (d) -2 The answer key says the answer is (a). But, I think all the answers can be...
4. ### Typo or math error?

Hello, everyone! I believe there was an error with the text of the following question, but I just want to make sure my math is perfect here and the text is really wrong: - Be a a real number so that 3y^2 - y + a = 0 have double roots. So, the solution to the following equation 3^{2x+1} - 3^x +...
5. ### Recursion or typo?

Hi there, new user here. would appreciate it alot if someone can help me out with this problem. I am looking at the solution and I cannot seem to figure out how they are going line by line. http://imgur.com/rgN69,ly9Qh see above, can someone please explain how they went from rec(n) =...
6. ### Mathematical Logic by Cori and Lascar : Possible typo?

I have a question on the textbook "Mathematical Logic: Propositional calculus, Boolean Algebras, predicate calculus" by Rene Cori and Daniel Lascar. On Lemma 1.6 on this page there is a part that says, "...if \mathcal{Y}(W) and \mathcal{Y}(V) are true, then \mathcal{Y}(\neg F), \mathcal{Y}(F...
7. ### Ring Theory Question (Typo?)

I'm doing a problem for homework out of my book "A First Course in Abstract Algebra 7th edition" (the problem is section 19 problem 30) and it reads as follows: This exercise shows that every ring R can be enlarged (if necessary) to a ring S with unity, having the same characteristic as R. Let...
8. ### Typo in the Birkhoff's book??

I must say that I mean russian edition of the book "Modern applied algebra (by G.Birkhoff and T.Bartee, ed. 1976)". Unfortunately, I couldn't find the original english edition (1970) but suspect that it has the same typo (or not?). On the page 25 it says: Let n(X) be the number of elements in...