Math problems in the third grade circle</p><p>Solution: estABlish a rectangular coordinate system with the center o of the semicircle as the coordinate origin and the straight line ab as the x axis, a

Math problems in the third grade circle

Solution: estABlish a rectangular coordinate system with the center o of the semicircle as the coordinate origin and the straight line ab as the x axis, a

Math problems in the third grade circle

Solution: estABlish a rectangular coordinate system with the center o of the semicircle as the coordinate origin and the straight line ab as the x axis, as shown in the above figure.

then what The equation of semicircle o is: x? +y？ = 1? ( 1≥y≥0)

Let the coordinates of point C be (a, b), then D(-a, b)? ，CD=2a？ Among them? (0≤a≤ 1，0≤a≤ 1)

Substitute D(-a, b) into the semicircle O equation to get a? +b？ = 1，b？ = 1-a？

∵AD=BC=x？ (x≥0)

∴x？ =b？ X for +( 1-a)？ = 1-a？ +( 1-a)？ =2-2a，？ 2a=2-x？

And AB=2.

∴y=2+2x+2-x？ =? -? x？ +2x+4

∫0≤a≤ 1，x=√(2-2a)

∴0≤x≤√2

∴y=-？ x？ +2x+4 (0≤x≤√2)

Mathematics related to Han Xin.

There are still 100 days before the college entrance examination. Math is so poor. I have never passed the exam and have no confidence in reviewing other subjects. Uncle, is there any quick and effect