If triangle ABC is similar to triangle DEF, which proportions correctly expresses the relationships between corresponding sides? FE FD СВ CA AB EF DE BC АВ DF EF AC EF ED BC AC

Please show me how to answer in excel. Questions 3-6.

What does the middle dot or point denote?

a and b are two points in the third dimension. Write an equation that describes the set of points that are equidistant to a and b. Draw a picture of this set in the case where a = i and b = j.