Second, in recent years, there are relatively few questions related to the circle in the finale, mainly quadratic functions and triangles and quadrilaterals, but questions related to the circle may still appear.
Third, the mathematics of the senior high school entrance examination, the test sites related to the circle mainly include several basic elements in the concept of the circle, such as diameter, radius, arc, chord, circumference angle, central angle, and the judgment conditions of the circle. The positional relationship between points and circles, and the positional relationship between straight lines and circles.
Fourthly, in the senior high school entrance examination, the common theorems related to circles mainly include the vertical diameter theorem, the chord center distance theorem of rounded corners and the tangent length theorem.
Fifth, the definition and property theorem of triangle inscribed circle, triangle circumscribed circle and circle inscribed quadrilateral.
Six, arc length, sector, bow, cylinder, cone related content and calculation formula must be mastered.
Seven, the common test questions mainly include the following:
1, the positional relationship between a point and a circle. This type of question usually gives you a coordinate system in fill-in-the-blank questions and multiple-choice questions, then there is a garden centered on a certain radius and a certain point, and then it is determined whether the point is inside or outside the circle.
2. The relationship between central angle, arc, chord and chord center distance. There may be general fill-in-the-blank and multiple-choice geometric proof questions. In an equal circle or the same circle, as long as a set of quantities of central angle, arc, chord and chord center distance are equal, other corresponding quantities are also equal.
3. The vertical diameter theorem and its inference. This kind of question type is very likely to appear. Generally, a right-angled triangle is constructed by connecting radius, the hypotenuse of the middle section is the radius of the right-angled triangle, and the two right-angled sides are half the chord length and center distance. Never use Pythagorean theorem to solve it.
4. The theorem of circle angle. The theorem of circumferential angle is based on the central angle, which can be used to prove the equal ratio or multiple relationship of angles. The circumference angle of the diameter is a right angle, and the chord of the right angle is the diameter. In the calculation of test questions with circle proof, auxiliary lines can be added to create conditions and be used flexibly, which is a simplification of the problem.
5. The positional relationship between a straight line and a circle. Generally appear in fill-in-the-blank questions and multiple-choice questions. According to the relationship between the distance d from the center of the circle to the straight line and the radius r of the circle. (1) d > r, phase separation. ②d=r, then tangency. ③ d < r, then it intersects.
6. The nature of tangent and the judgment theorem of tangent. This is a very common test center. The general method to prove tangency is to make radius and prove verticality, or to make verticality and prove radius.
7. Tangent length theorem. Common test sites. Note that tangent length and tangent are two completely different concepts.
8. The inscribed circle of a triangle. When solving the problem of tangency between triangle and circle, tangent length theorem and pythagorean theorem are often used to find the length of radius through column equation.
9. Find the arc length and sector area. There are also many questions in this exam. Remember the formula for calculating arc length and the formula for calculating sector area.
10, bow, cylinder side development diagram, cone side development diagram lateral area calculation of several cones. This question type must be mastered.