\(\overrightarrow{n_{d1}}=\left(2;-1\right)\) ; \(\overrightarrow{n_{d2}}=\left(1;-3\right)\)
\(cos\left(d_1;d_2\right)=\frac{\left|2.1+\left(-1\right).\left(-3\right)\right|}{\sqrt{2^2+\left(-1\right)^2}.\sqrt{1^2+\left(-3\right)^2}}=\frac{5}{5\sqrt{2}}=\frac{\sqrt{2}}{2}\)
\(\Rightarrow\left(d_1;d_2\right)=45^0\)