CN203415136U

CN203415136U - Middle school mathematics cross line theorem demonstration teaching instrument

Info

Publication number: CN203415136U
Application number: CN201320574238.6U
Authority: CN
Inventors: 李广普
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-09-04
Filing date: 2013-09-04
Publication date: 2014-01-29
Anticipated expiration: 2023-09-04

Abstract

The utility model discloses a middle school mathematics cross line theorem demonstration teaching instrument which is characterized in that a linear chute with scales is formed in a circular chute along the direction of a central cross line; a lower arced sliding block and an upper arced sliding block are oppositely arranged inside the circular chute; a rectangular sliding block is arranged inside the linear chute with the scales; the rectangular sliding block, the lower arced sliding block and the upper arced sliding block are all in independent rotation connection with a straight rod with scales. Due to adoption of the teaching instrument, the quantitative relationship between the cross line length and two line lengths from a point to a secant line and to an intersection point is clearly demonstrated when the cross line and the secant line of a circle are made through the point outside the circle, therefore, the cross line theorem can be visibly verified, the learning interest of students is stimulated, and a good assistance effect is achieved for teachers in teaching.

Description

Middle school mathematics line of cut theorem demonstration teaching aid

Technical field:

The utility model relates to middle-school mathematics teaching apparatus.

Background technology:

In middle-school mathematics teaching process, line of cut theorem is an important knowledge point.Teachers' instruction often will motivate students' interest in learning by teaching aid while importing knowledge.Yet currently lack a kind of demonstration teaching aid for this theorem, be unfavorable for that student understands this theorem of study intuitively, is also unfavorable for the importing of problem and motivates students' interest in learning.

Summary of the invention:

The purpose of this utility model is just to provide a kind of new teaching apparatus for mathematics, and it can solve in existing middle-school mathematics teaching effectively because the demonstration teaching aid lacking for line of cut theorem is unfavorable for that student learns the problem of this theorem intuitively.

The purpose of this utility model is achieved in that middle school mathematics line of cut theorem demonstration teaching aid, it is characterized in that: at the straight line chute of concentric stroking groove center line tangential direction mounting strap scale, in circular chute, arc lower slide block and upper arc shaped slider are installed in opposite directions, with rectangle slide block is installed in the straight line chute of scale, rectangle slide block, arc lower slide block and upper arc shaped slider are all realized and being rotationally connected separately with the straight-bar with scale.

The beneficial effects of the utility model are: can clearly reflect when outside circle, any makes round tangent line and secant, length of tangent line and this point are to the quantitative relation between secant and two length along path of circle intersection point, thereby verify intuitively line of cut theorem, thereby motivate students' interest in learning, teacher's teaching is played to good booster action.

Accompanying drawing explanation:

Fig. 1 is structural representation of the present utility model, and Fig. 2 is mathematical principle figure of the present utility model.Below in conjunction with accompanying drawing, the utility model is further described.

Embodiment:

Fig. 1 shows middle school mathematics line of cut theorem demonstration teaching aid of the present utility model,

Straight line chute 2 at the centerline tangent direction mounting strap scale of circular chute 1, in circular chute 1, arc lower slide block 5 and upper arc shaped slider 6 are installed in opposite directions, with the interior installation rectangle of straight line chute 2 slide block 4 of scale, rectangle slide block 4, arc lower slide block 5 and upper arc shaped slider 6 are all realized and being rotationally connected separately with the straight-bar 3 with scale.Arbitrary slide block of slip rectangle slide block 4, arc lower slide block 5 and upper arc shaped slider 6, all the other slide blocks move thereupon.By the scale mark of the straight-bar 3 with scale, read rectangle slide block 4 and to length, the rectangle slide block of line segment between point of contact, within 4 minutes, be clipped to the length of line segment between arc lower slide block 5 and upper arc shaped slider 6, analyze the quantitative relation of three data, thereby verified intuitively line of cut theorem.Conventionally in the situation that chute width and slide block length can not be ignored, should using slide block center as the end points reading of line segment, prevent larger error.

In Fig. 2, B, C, D point are respectively the centers of three slide blocks, and O point is the two concentrically ringed centers of circle that form circular chute.Dashed line segment AB is

tangent line, straight line BD hands over

in a C, D.According to line of cut theorem, there is AB ²=BCBD is mathematical principle of the present utility model.

Claims

1. a middle school mathematics line of cut theorem demonstration teaching aid, it is characterized in that: at the straight line chute (2) of circular chute (1) centerline tangent direction mounting strap scale, in circular chute (1), arc lower slide block (5) and upper arc shaped slider (6) are installed in opposite directions, with rectangle slide block (4) is installed in the straight line chute (2) of scale, rectangle slide block (4), arc lower slide block (5) and upper arc shaped slider (6) are all realized and being rotationally connected separately with the straight-bar (3) with scale.