As shown in the figure, a and B are separated by the lake water, and Ca = 50m, CB = 60m, ∠ ACB = 145 ° are measured from C. draw the figure as shown in the figure with 1cm representing 10m (i.e. 1:1000 scale). Measure the length of AB (accurate to 1mm), and then convert the actual distance between a and B

As shown in the figure, a and B are separated by the lake water, and Ca = 50m, CB = 60m, ∠ ACB = 145 ° are measured from C. draw the figure as shown in the figure with 1cm representing 10m (i.e. 1:1000 scale). Measure the length of AB (accurate to 1mm), and then convert the actual distance between a and B

As shown in the figure, the measured length of AB is about 10.5cm, and the actual distance is about 10.5 × 1000 = 10500cm = 105m. That is to say, the actual distance between a and B is 105m

In ⊙ o, AB is the diameter, CD bisects ⊙ ACB intersects ⊙ o with D, and Ca + CBCD = 2

It is proved that if a is used as am ⊥ CD and B is used as BN ⊥ CD, the perpendicular feet are m and N, respectively, ∵ AB is the diameter, CD bisects ⊙ ACB intersects ⊙ o in D, ∵ ACD = ⊙ BCD = 45 °, both ∵ ACM and △ BCN are isosceles right triangles, ad = BD, CM = 22ac in RT △ ACM, CN = 22bc in RT △ BCN, ∵ cm + CN = 22 (AC

As shown in the figure, ⊙ o is the circumscribed circle of △ ABC, the chord CD bisects ∠ ACB, ∠ ACB = 90 ° to verify: Ca + CB = 2CD

It is proved that: connecting ad, BD, passing a as am ⊥ CD, passing B as BN ⊥ CD, the perpendicular feet are m, N, ∵ AB as diameter, CD bisects ⊙ ACB intersects ⊙ o in D, ∵ ACD = ∵ BCD = 12 ⊙ ACB = 45 °, both ∵ ACM and △ BCN are isosceles right triangles, ad = BD, CM = 22ca in RT △ ACM, CN =