  For a multi-attribute decision making (MADM) problem, the information of
alternatives under different attributes is given in the form of intuitionistic
fuzzy number(IFN). Intuitionistic fuzzy set (IFS) plays an important role in
dealing with un-certain and incomplete information. The similarity measure of
intuitionistic fuzzy sets (IFSs) has always been a research hotspot. A new
similarity measure of IFSs based on the projection technology and cosine
similarity measure, which con-siders the direction and length of IFSs at the
same time, is first proposed in this paper. The objective of the presented
pa-per is to develop a MADM method and medical diagnosis method under IFS using
the projection technology and cosine similarity measure. Some examples are used
to illustrate the comparison results of the proposed algorithm and some
exist-ing methods. The comparison result shows that the proposed algorithm is
effective and can identify the optimal scheme accurately. In medical diagnosis
area, it can be used to quickly diagnose disease. The proposed method enriches
the exist-ing similarity measure methods and it can be applied to not only
IFSs, but also other interval-valued intuitionistic fuzzy sets(IVIFSs) as well.
