As shown in the figure, in the two concentric circles with o as the center, the chord AB and CD of the big circle are equal, and AB and the small circle are tangent at point E

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• 1. As shown in the figure, it is known that in △ AOB, ∠ AOB = 90 ° OD ⊥ AB is at point D. the circle with point o as the center and OD as the radius intersects OA at point E, intercept BC = ob on Ba, and prove that CE is the tangent of ⊙ o
• 2. As shown in the figure, ⊙ o radius OA is the diameter of ⊙ O1, ⊙ o another radius OC intersection ⊙ O1 and point B, try to explain the arc length relationship between chord AB and chord AC
• 3. As shown in the figure, OA, ob, OC are ⊙ o radius - AC = - BC, D, e are OA, ob, are the midpoint CD and CE equal? Why is it as shown in the figure
• 4. As shown in the figure, in RT △ AOB, the circle AB with radius OA intersects at point C. If Ao = 5, OB = 12, the length of BC is obtained
• 5. In the R T triangle AOB, ∠ o = 90 degrees, OA = 6, OB = 8, take o as the center of the circle, OA as the radius, make the circle AB to C, and find the length of BC?
• 6. As shown in the figure, in RT △ AOB, the circle AB with radius OA intersects at point C. If Ao = 5, OB = 12, the length of BC is obtained
• 7. As shown in the figure, in RT △ AOB, ∠ B = 40 °, take OA as radius, O as center, make ⊙ o, intersect AB at point C, intersect ob at point D. calculate the degree of CD
• 8. As shown in the figure, it is known that point O is a point on the hypotenuse of RT △ ABC, with point o as the center and OA length as the radius, the center O and BC are tangent to point E As shown in the figure, we know that the point O is a point on the hypotenuse AC of ABC of RT triangle. With the point o as the center and the OA length as the radius, the center O and BC are tangent to point E and intersect with AC at point D, connecting AE. (1) proof: AE bisection angle CAC (2) explore the quantitative relationship between angle 1 and angle C in the figure Just ask the second question, the first question I know
• 9. As shown in the figure, in the known RT △ ABC, the ⊙ o cross bevel BC with ab as the diameter is at point D, and E is the midpoint of AC. connect ed and extend the extension line of intersection AB at point F. (1) prove that De is the tangent of ⊙ o; (2) if ⊙ f = 30 ° AB = 4, find the length of DF and ef
• 10. Given that the circle C and the y-axis intersect at two points m (0. - 2), and the center of the circle C is on the straight line 2x-y-6 = 0, the equation of circle C is obtained
• 11. As shown in the figure, the center of two concentric circles is O, the radius of big circle O is OA, OB intersects small circle O with C, D, please explain: AB / / CD I hope we don't use center angle and circle angle
• 12. As shown in the figure, BD is the diameter of ⊙ o, OA ⊥ ob, M is the point on the inferior arc AB, through point m as the tangent of ⊙ o, the extension line of OA at point P, MD and OA at point n. (1) verification: PM = PN; (2) if BD = 4, PA = 32ao, through point B as BC ∥ MP intersection ⊙ o at point C, the length of BC
• 13. As shown in the figure, BD is the diameter of ⊙ o, OA ⊥ ob, M is the point on the inferior arc AB, through point m as the tangent of ⊙ o, the extension line of OA at point P, MD and OA at point n. (1) verification: PM = PN; (2) if BD = 4, PA = 32ao, through point B as BC ∥ MP intersection ⊙ o at point C, the length of BC
• 14. As shown in the figure, the radius of the inscribed circle of RT △ ABC is 1 cm, and the hypotenuse is tangent to the circle O at point D. given AB = 5, find the length of AD and AC
• 15. If the side length of equilateral △ ABC is 3cm, the radius of its inscribed circle is
• 16. As shown in the figure, circle O is the inscribed circle of triangle ABC, and the tangent points are D, e, F. the known angles BCA = 90 degrees, ad = 5cm, DB = 3cm. Find the area of triangle ABC D is on AB, e is on BC, f is on AC
• 17. As shown in the figure, it is known that in RT △ ABC, the radius of the inscribed circle is 3cm and the radius of the circumscribed circle is 12.5cm, so the three sides of △ ABC can be calculated
• 18. The diameter of the circle O of BD, OA perpendicular to ob, M is a point on the inferior arc AB, the tangent MP of the circle O crosses through point m, the extension line of OA intersects at point P, and the intersection of MD and OA intersects at point n 1. Verify PM = PN. 2. If BD = 4, PA = two-thirds Ao, make BC ∥ MP through point B, intersect circle O at point C, and find the length of BC.
• 19. OC in circle O is perpendicular to ab AB = 16 sinaoc = 3 / 5 calculate radius OA of circle O and chord center distance OC calculate cosaoc tanaoc
• 20. Given the radius of ⊙ o OA = 5, the chord center distance OC of chord AB = 3, then AB = () A. 4B. 6C. 8D. 10