Answer:
[tex]m\angle F\approx 100^{\circ}[/tex]
Step-by-step explanation:
For any triangle, the Law of Cosines is given by [tex]c^2=a^2+b^2-2ab\cos C[/tex], where all three variables are interchangeable.
Therefore, we have:
[tex]f^2=g^2+h^2-2gh\cos F,\\960^2=380^2+820^2-2(380)(820)\cos F,\\\cos F=-\frac{131}{779},\\F=\arccos(-\frac{131}{779})\approx \boxed{100^{\circ}}[/tex]
