Tolong bantu dengan caranya, makasih!!

[tex] \cos \beta = \frac{sa}{mi} \\ \cos( {45}^{0} ) = \frac{40}{mi} \\ \frac{1}{2} \sqrt{2} = \frac{40}{mi} \\ mi \sqrt{2} = 40 \\ mi = \frac{80}{ \sqrt{2} } = 40 \sqrt{2} [/tex]