2. Draw a ray of 3 angles, 2 rays of 6 angles, 3 rays of 10 angle and 4 rays of 13 angle. If you draw n rays in ∠AOB, how many angles will be formed?
3. The bisector of ∠AOB is OM, ON is a ray in ∠MOA, OG is a ray outside ∠ AOB, ∠GOB is a right angle, and everything else is in ∠GOB. After careful analysis, a classmate came to the conclusion that a relationship is ∝. If it is correct, please write down the process of reaching this conclusion.
4. Stack a pair of right-angled triangular plates together, so that the right-angled vertex coincides with point O, then ∠ AOB+∠ Doc = ().
5. Student A starts from A and walks 75 northeast 10 m to B, while student B starts from A and walks southwest 15 m to C. Then the included angle between AB and AC is ().
6. Given that point O is on straight line AB, the length of line segment OA is 4cm, the length of line segment OB is 6 cm, and e and f are the midpoint of line segments OA and OB respectively, then the length of line segment EF is () cm.
7. ∠AOB = 90, OC is the light outside ∠ AOB, OE is the bisector OF ∠BOC, and of is the bisector of ∠AOC. The number of times to find ∠EOF.