Outside the high school program / Transformations 14 exercises (including 13 corrected)

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ABCDEFGH OABCDE 1. Isometry E.2627 The figure below shows two quadrilat-erals ABCD and EFGH : 1 Take the necessary measurements to complete the table below : AB BC CD DA Mesure (en cm ) EF FG GH HE Mesure (en cm ) 2 a Draw the straight lines ( AE ) , ( BF ) , ( CG ) and ( DH ) . What do you notice? b Name O the point of intersection of these straight lines. c Complete the tables below : OA OB OC OD Mesure (en cm ) OE OF OG OH Mesure (en cm ) d What do you notice? E.2628 Consider the polygon ABCDE below and O a point in the plane. 1 a Place the point A on the half-right [ OA ) such that : OA = 2 · OA b Place the point B on the half-right [ OB ) such that : OB = 2 · OB c Do the same with points C , D and E . d Draw the polygon A B C D E 2 a Perform the following measurements : AB BC CD DE EA Mesure (en cm ) A B B C C D D E E A Mesure (en cm ) b What can you say about these two polygons? 3 a What conjecture can you make about the straight lines ( AB ) and ( A B ) ? b Which theorem confirms your conjecture? https://chingmath.fr chapExoCorrec/2627 sacados/2627 ABCDEFGH chapExoCorrec/2628 sacados/2628 OABCDE
MNIJ ABCDE OPI(dNM(dNMCC ABG E.2632 A road is to be built from town M to town N . This road has to pass over a river: the bridge will be perpen-dicular to the riverbed. Place the bridge (more precisely the points I and J ) so that the length of the road is minimal. Hint : think of the triangular inequality. E.2645 Consider the five points of the plane shown below : 1 Determine the center and ratio of the homothety trans-forming A into C and B into D . 2 Determine the center of the homothety of ratio 3 2 trans-forming the point B into the point A . 3 Justify that there are no homotheties transforming B into C and D into E . E.2646 Consider two points in the plane O and P separated by 1 cm ; the circle C has the point O as its cen-ter and a radius of 3 cm ; the circle C has center P and radius 2 cm . Let I be the point of intersection of the straight line ( OP ) with the circle C . The straight line ( d ) passing through I intercepts the circles C and C at M and N respectively. The straight line ( d ) passing through I is secant to the circle C at M and also intersects the circle C at N . 1 Show that the point I also belongs to the circle C . What can you tell from the relative position of the two circles C and C . 2 Determine the center and ratio of the homothety trans-forming the circle C into the circle C . 3 Deduce that the straight lines ( NN ) and ( MM ) are parallel. E.573 Let C be a circle of center O and A a point of the circle. Consider the point M running through the circle C and I the middle of the segment [ OM ] What does the point I describe when the point M describes the circle C ? E.574 Construct, in the figure below, the point C such that ABC has as center of the inscribed circle (the point of intersection of the bisectors) the point G . https://chingmath.fr chapExoCorrec/2632 sacados/2632 MNIJ chapExoCorrec/2645 sacados/2645 ABCDE chapExoCorrec/2646 sacados/2646 OPI(dNM(dNMCC chapExoCorrec/573 sacados/573 chapExoCorrec/574 sacados/574 ABG
AMOC ABMNIC MNIJ OABCD E.1839 Consider a circle C , a point A C and a point M that describes the circle: i.e. the position of M is variable and it will travel the circle C . Consider the point I middle of [ AM ] . 1 Place the point I on the figure above. 2 a Place the point M diametrically opposite the point A . Where then is the point I . b If the point M lies in A , where is the point I . c Place the point M at four other possible locations and construct the associated point I each time 3 When the point M describes the entire circle C which set describes the point I . E.1852 Consider a circle C of diameter [ AB ] . Let M and N be two points of C distinct from A and B . 1 Place on the figure above the point J intersection of the straight lines ( NB ) and ( MA ) . 2 Show that the straight line ( IJ ) is perpendicular to ( BA ) . E.1854 A road is to be built from town M to town N . This road has to pass over a river: the bridge will be perpen-dicular to the riverbed. Place the bridge (more precisely the points I and J ) so that the length of the road is minimal. Hint : think of the triangular inequality. E.1869 Consider the two triangles OCD and OAB rectangles isosceles at O By means of a rotation, the characteristics of which will be indicated, show that the segments [ CA ] and [ DB ] have the same length. https://chingmath.fr chapExoCorrec/1839 sacados/1839 AMOC sacados/1852 ABMNIC chapExoCorrec/1854 sacados/1854 MNIJ chapExoCorrec/1869 sacados/1869 OABCD
ABCDEF ABCMM1M2M E.1870 Consider a rectangle ABCD , M a point on [ DC ] , and N a point on [ BC ] . Determine, in the figure above, the positions of points M and N such that the path passing through points E , M , N , and F is as short as possible. (No justification is required) . 2. Isometry compound E.2631 Let A , B , C be three distinct two-by-two points in the plane and M be any point in the plane. The figure opposite represents the image M of M by the transformation SCOPY 01 S B S A where : S A ( M ) = M 1 ; S B ( M 1 ) = M 2 ; S C ( M 2 ) = M Determine, if they exist, the invariants of the transformation S C S B S A . E.2633 Consider in the plane a square ABCD . Let I be the midpoint of [ AB ] . 1 Simplify the writing of the following transformation : t AB t CA t AC t BC 2 Establish the following relationship : t BC S I S B = t BD 3 Determine the point M verifying the following relation-ship : S I S B = S M S C https://chingmath.fr chapExoCorrec/1870 sacados/1870 ABCDEF chapExoCorrec/2631 sacados/2631 ABCMM1M2M chapExoCorrec/2633 sacados/2633