3 Abird is sitting on the top of a 80 m high tree. From a point on the

1.	3 Abird is sitting on the top of a 80 m high tree. From a point on the ground, the angle of elevation ofa bird is45 The bird flies away from the point of observation horizontally and remains at a constant'height. Afier 2seconds, the angle of elevation of the bird from the point of observation becomes 30. Find the speed of flying4of the bird. (Use 3 1.7)
Answer» In triangle OAC tan 45=AC/OA=1 AC=OA=80 IN TRIANGLE ODB tan 30=BD/OB=1/√ 3 OB=BD√ 3-AC√ 3(since ac=bd as bird remains constant height) AB=OB-OA=AC√ 3-AC=AC(√ 3-1)=80(√ 3-1) NOW FOR 2 SEC 80(√ 3-1)/2=40(√ 3-1) =29.2M/SEC

3 Abird is sitting on the top of a 80 m high tree. From a point on the ground, the angle of elevation ofa bird is45 The bird flies away from the point of observation horizontally and remains at a constant'height. Afier 2seconds, the angle of elevation of the bird from the point of observation becomes 30. Find the speed of flying4of the bird. (Use 3 1.7)

Answer»

In triangle OAC tan 45=AC/OA=1

AC=OA=80

IN TRIANGLE ODB

tan 30=BD/OB=1/√ 3

OB=BD√ 3-AC√ 3(since ac=bd as bird remains constant height)

AB=OB-OA=AC√ 3-AC=AC(√ 3-1)=80(√ 3-1)

NOW FOR 2 SEC

80(√ 3-1)/2=40(√ 3-1)

=29.2M/SEC