1) a- provide the definition of frechet derivative of a map f: v_{1}\rightarrow v_{2} where (v_{i},||.||_{i}) are finite dimentional normed vector spaces.
b- let f: r^{2}\rightarrow r be defined by
f(x)=x_{1}x_{2} if x_{1}x_{2}\epsilon q
f(x)=0, if x_{1}x_{2}\notin q
decide f has a directional derivative along all v\in r^{2} .
decide f is frechet defferential at (0,0).