Current location - Training Enrollment Network - Mathematics courses - What mathematical problems can be solved by using the properties of parallel lines?
What mathematical problems can be solved by using the properties of parallel lines?
Use the properties of parallel lines: two straight lines are parallel and the same angle is equal. To prove

It is proved that the sum of the internal angles of a triangle is equal to 180.

Feeling: In △abc, ∠a, ∠b and ∠c are three internal angles. To prove ∠a+∠b+∠c= 180, that is to say ∠A+∞. Using the characteristics of parallel lines, it is necessary to draw a parallel line through point A to achieve the goal.

A is ef BC.

∠b=∠ 1,∠ C = ∠ 2。 (Two straight lines are parallel with equal internal angles).

∠ 1+∠bac+∠2= 180,

∠ B+∠ BAC+∠ C = 180。 (Equivalent substitution)

Can't draw.