Answer:
5.7
Step-by-step explanation:
We can use the Law of Cosines to answer this question
[tex]\begin{array}{rcl}e^{2} & = & d^{2} + f^{2} - 2df \cos E \\& = & 10^{2} + 7^{2} - 2 \times 10\times 7 \times \cos 34^{\circ}\\& = & 100 + 49 - 140\times 0.8290\\& = & 149 - 116.1\\& = & 32.9\\ e & = & \textbf{5.7}\\\end{array}[/tex]