双1次曲面
u {\displaystyle u} 方向および v {\displaystyle v} 方向の偏微分は,以下の通り。
∂ N 0 ∂ u = − 1 4 ( 1 − v ) {\displaystyle {\frac {\partial N_{0}}{\partial u}}=-{1 \over 4}(1-v)}
∂ N 1 ∂ u = 1 4 ( 1 − v ) {\displaystyle {\frac {\partial N_{1}}{\partial u}}={1 \over 4}(1-v)}
∂ N 2 ∂ u = 1 4 ( 1 + v ) {\displaystyle {\frac {\partial N_{2}}{\partial u}}={1 \over 4}(1+v)}
∂ N 3 ∂ u = − 1 4 ( 1 + v ) {\displaystyle {\frac {\partial N_{3}}{\partial u}}=-{1 \over 4}(1+v)}