how to use static lib on linux

i compiled static taglib,i got libtag.a file.i copy this file to project dir.and i added some code in .pro

Code:

---

TAGLIBDIR = /usr/local
INCLUDEPATH += $$(TAGLIBDIR)/include
LIBS += libtag.a

---

whe i run my pro.the tell me:

Code:

---

error: libtag.a: No such file or directory

---

why?and how?