As observed from the top of a lighthouse, 100 m high above sea level, the angle of depression of a ship sailing directly towards it, changes from 30°
to 60°. Determine the distance travelled by the ship during the period of observation. 
.
Sol.
Let AB be the lighthouse, C and D be the two points.
Q. 28. Prove that the ratio of the areas of two similar triangles is equal to the ratio of squares of their corresponding sides. Using the above result, prove the following :
If D is a point on the side AB of ΔABC such that
AD : DB = 3 : 2 and E is a point on BC such that
DE||AC; find the ratio of the areas of ΔABC and ΔBDE.
| Mathematics 2008 Question Papers Class X | |||||||
| Delhi | Outside Delhi | Compartment Delhi | Compartment Outside Delhi | ||||
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