2.3.34 Gradient and directional derivative

condition: For a given function \( z(x, y) \) find: a) \( d z \) b) \( \left.\operatorname{grad} z\right|_{M} \), c) \( |\operatorname{grad} z|_{M} \mid\). \[ z=e^{x} \cdot \cos y, \quad M(1; 0) \]