TY  - JOUR
AU  - Kannappan, PL
TI  - A Functional Equation for the Cosine
JO  - Canadian mathematical bulletin
PY  - 1968
SP  - 495
EP  - 498
VL  - 11
IS  - 3
UR  - http://geodesic.mathdoc.fr/articles/10.4153/CMB-1968-059-8/
DO  - 10.4153/CMB-1968-059-8
ID  - 10_4153_CMB_1968_059_8
ER  -