Question 891900
Assuming the triangle might not be a Right Triangle, find the distances or lengths for DE, EF, and FD, and use Law Of Cosines.


If you just use some variable, m for the angle DEF, then form:
{{{highlight_green((EF)^2+(ED)^2-2(EF)(ED)*cos(m)=(DF)^2)}}};
solve for m.