okay

220k hits

I think Rene's analysis is correct, but I think it should be included as an expression. It's one of those things that someone could want to look up, and should have a reasonable chance of finding it.

@@ -7,0 +7,3 @@
+<k_ele>
+<keb>成す角</keb>
+</k_ele>
@@ -11,1 +14,3 @@
-<pos>&n;</pos>
+<pos>&exp;</pos>
+<s_inf>often ...のなす角</s_inf>
+<gloss>formed angle</gloss>
@@ -13,1 +18,0 @@
-<gloss>formed angle</gloss>

eij
    ～のなす角度の余弦に比例する
    be proportional to the cosine of the angle between
    AとBとのなす角度として定義される
    be defined as the angle between A and B
    二つのベクトルのなす角
    an angle between two vectors
    二つのベクトルのなす角を求める
    calculate the angle between two vectors《数学》

not sure, but i think this is based on an incorrect parsing.  の is filling in for が here as it sometimes does when acting prenominally.

so 二つのベクトルのなす角 is parsed as [二つのベクトルのなす]角, not as 二つのベクトルの[なす角].  there's already an entry for the verb なす.

Sorry, no references, a Japanese person told me what this means.

example: 
the angle made between line A and line B
線Aと線Bのなす角

なす is another reading of 作る