Combinatorics/Multinomial coefficients

Subpage for alternate proofs
/Proofs

Henderson, Kenneth B., et al. Modern Geometry: Its Structure and Function. McGraw-Hill, 1962.

Crangle, Eva A. The Mathematics Teacher, vol. 56, no. 5, National Council of Teachers of Mathematics, 1963, pp. 359–61, http://www.jstor.org/stable/27956853.

Quotes from the review:

Here is a textbook that can be used equally well by traditionally minded teachers and by those who are oriented to "modern mathematics."

The book is primarily written from a traditional, expository point of view. However effort is made ot use discovery methods when the student is asked to "state and prove your own theorems" and to "prove or disprove" a statement.