In the known triangle ABC, ad is the middle line. Prove AD & # 178; = (1 / 2) (AB & # 178; + AC & # 178;) - (BC / 2) &# 178;

RELATED INFORMATIONS

• 1. In the triangle ABC, D is the midpoint of the BC side, and it is proved that AD & # 178; = 1 / 2 (AB & # 178; + AC & # 178;) - 1 / 4 (BC & # 178;) It's all vectors
• 2. As shown in the figure, in triangle ABC, ∠ ACB = 60 ° AC ＞ BC, there are triangle ABC ', triangle BCA', triangle cab ' Better be more detailed
• 3. Given the isosceles triangle ABC, the base BC = 20, D is a point on AB, and CD = 16, BD = 12, find the length of AD
• 4. In the inner △ ABC of ⊙ o, if OD ⊥ BC is at point D, ∠ BOD = 36 °, then the degree of ⊙ A is
• 5. As shown in the figure, ⊙ o is the circumscribed circle of △ ABC, the chord CD bisects ∠ ACB, ∠ ACB = 90 ° to verify: Ca + CB = 2CD
• 6. As shown in the figure, the circle O is the circumscribed circle of △ ABC, the radius of circle O is 2, SINB = three quarters, then the length of chord AC is
• 7. It is known that AB is the diameter of circle O, the chord center distance of chord BC is 4, then the length of AC is? Do me a favor
• 8. In the triangle ABC, ab = AC, angle BCA = 80 degrees, O is a point in the triangle ABC, and the angle OBC = 10 degrees, angle oca-20 degrees
• 9. In the triangle ABC, ab = AC, BAC = 80 degrees, O is a point in the triangle ABC, OBC = 10 degrees, OCA = 20 degrees The picture shows
• 10. In the triangle ABC, there is a point O, OA = 3cm, OB = 4cm, OC = 5cm, find (1) ∠ AOB, ∠ AOC degree (2) find the respective area of triangle AOB, AOC, BOC emergency
• 11. BD is the bisector of angle ABC, De is perpendicular to AB and E, DF is perpendicular to BC and F, area of triangle ABC = 36, ab = 18, BC = 12, find the length of De and DF
• 12. In △ ABC, ab = 5cm, BC = 7cm, AC = 8cm. Draw three circles with a, B, C as the center respectively, and make them circumscribed, then the radius of ⊙ A is cm, In △ ABC, ab = 5cm, BC = 7cm, AC = 8cm. Draw three circles with a, B, C as the center, and make them two outside Then the radius of ⊙ A is cm, the radius of ⊙ B is cm, and the radius of ⊙ C is cm
• 13. In the triangle ABC, ab = 5, BC = 8 and AC = 7. Take a, B and C as the center respectively. Draw three circles and make them circumscribe each other. Find the radius of circle a, circle B and circle C
• 14. It is known that the lengths of three sides of a triangle are 4cm, 5cm and 6cm respectively. The three circles centered on each vertex are tangent to each other, and the radii of the three circles are calculated most urgent
• 15. As shown in the figure, △ ABC is inscribed on the circle O, ab = AC, cos ∠ ABC = four fifths. If the radius of circle O is 5cm, calculate the area of △ ABC (2) If BD bisector angle ABC, ah ⊥ CD is in H, find HC: BD
• 16. If AB = 3cm, AC = 4cm, ad = 2.5cm, find the radius of circle o
• 17. It is known that the isosceles triangle ABC is inscribed on the circle O with radius 5. If the length of the bottom edge BC is 6, then the tangent of the bottom angle is 0
• 18. It is known that the length of the base of the isosceles triangle ABC is 10cm and the vertex angle is 120 degrees. Find the diameter of its circumscribed circle
• 19. If the waist length of the isosceles triangle ABC is 3cm and the vertex angle is 120 degrees, the diameter of its circumscribed circle is
• 20. Known: as shown in the figure, in the isosceles subangular triangle ABC, D is the midpoint of the hypotenuse AB, P is on BD, PM is perpendicular to BC, m, PN is perpendicular to AC, N, DM is equal to DN