We present a careful and detailed light curve analysis of publicly available I -band data on fundamental mode RR Lyrae ( RRab ) stars of the Large Magellanic Cloud ( LMC ) obtained by the Optical Gravitational Lensing Experiment ( OGLE ) phase-III project .
Using the Fourier parameters of 13 , 095 RRab stars , metallicities and absolute magnitudes of individual stars are obtained .
The representation of stars on the P - \phi _ { 31 } ^ { V } plane shows the existence of three significant metallicity groups with mean metallicities as -1.20 \pm 0.12 dex , -1.57 \pm 0.10 dex and -1.89 \pm 0.09 dex .
The corresponding absolute magnitudes of these three groups are obtained as 0.70 \pm 0.08 mag , 0.59 \pm 0.06 mag and 0.49 \pm 0.08 mag , respectively .
Distribution of these three groups as a function of vertical |z| distance indicates that the formation of the LMC disk predates the formation of the inner halo .
Issue of the existence of a metallicity gradient as a function of galactocentric distances has also been addressed .

Approximating the structure of the LMC disk as a triaxial ellipsoid , the inclination angle ( i ) relative to the plane of the sky and the position angle of the line of nodes ( \theta _ { lon } ) were estimated as 24 ^ { \circ } .20 and 176 ^ { \circ } .01 , respectively .
The axes ratios and the eccentricity were also determined using the principal axes transformation method .