2. As shown in the figure, the straight line AB and CD intersect at point O, and if ∠AOC = 90°, the positional relationship between AB and CD is perpendicular to each other; If AB⊥CD is kept, ∠ AOC = ∠ COB = ∠ BOD = ∠ AOD = 90.
3. As shown in the figure, straight lines AB and CD intersect at oe⊥ab o, and the vertical foot is O ... If EOD = 43, AOC = 47.
4. As shown in the figure, it is known that DE and BC intersect at point O, AO⊥BC intersect at point O, and ∠ 1=2∠2+0 = 60, ∠ 2 = 30, ∠ 3 =.
5: Draw a vertical line of a line segment later, with the vertical foot at (D)
A. On the line segment
B. At the endpoint of the line segment
C. On the extension line of the line segment
D. all of the above are possible
6. As shown in the figure, ∠ BAC = 90, and AD⊥BC is at point D, then the correct numbers in the following conclusions are (two, ① ④).
① The vertical line from point B to AC is line AB; ② Line segment AC is a vertical line segment from point C to point AB; ③ The line segment AD is a vertical line segment from point D to BC; ④ The line segment BD is a vertical line segment from point B to AD.
A. 1
B.2 this is correct.
C.3
Dingsi
7: As shown in the figure, if AO⊥BO is at point O, the straight line CD passes through point O, and ∠ AOD = 140, then the degree of ∠BOD is (b).
A. 120
B 130
C. 140
D. 150
8. As shown in the figure, straight lines AB and CD intersect at point O, and OE is a straight line. If ∠1= 30 and ∠ 2 = 60, the positional relationship between OE and AB is perpendicular to each other, which is recorded as OE ∠ AB because ∠ AOE = 90.
9. As shown in the figure, it is known that AO⊥OC is at point O and BO⊥DO is at point O, then ∠ 1=∠3.
10: As shown in the figure, AD⊥CD is at point D, BC⊥AC is at point C. Given AB=4 and CD=2, the value range of line segment AC is: 2.