Current location - Training Enrollment Network - Mathematics courses - Senior high school requires two mathematical geometry proofs, such as triangular prism ABC-A 1 b1c1,in which the bottom is the side of a regular triangle with a side length of 21.
Senior high school requires two mathematical geometry proofs, such as triangular prism ABC-A 1 b1c1,in which the bottom is the side of a regular triangle with a side length of 21.
It is proved that the midpoint of (1)EC is set as G point, because EC=2BF, BF is parallel to EG, and the quadrilateral EFBG is a parallelogram, so BG is parallel to EF; (parallelogram decision theorem)

(2) If BM is parallel to plane AEF and plane BGM is parallel to plane AEF, then GM is parallel to AE; (Two parallel planes are parallel to the straight line cut by the third plane)

(3) From the above, it can be seen that GM is parallel to AE and G is the midpoint of EC, so GM is a midline of triangle AEC, so M is the midpoint of AC. (midline theorem)

The method is as above. For specific theorems, you can find the original text in the math book.