A comparison of the temperature distributions along the wall and center of the fin and the heat loss from the fin, computed assuming the fin tip is insulated and assuming it is not insulated in a triangular fin, is performed by the two-dimensional forced analytic method. When the fin tip is not insulated, a comparison between forced analytic method and analytic method is made in the heat loss and temperature along the fin wall. The value of Biot number varies from 0.01 to 1.0. The root temperature and surrounding convection coefficients of the fin are assumed as a constant. The results are (1) the analysis on the triangular fin assuming the fin tip is insulated does not produce a good value as compared to that of not-insulated case as the non-dimensional fin length decreases and as the value of Biot number increases and (2) the errors between forced analytic method and analytic method are very small, but the former method is better for computer running time and accuracy.