1.

EXAMPLE 16 If in a A ABC, sin A, sin B and sin C are in AP,then(a) the altitudes are in A.P. (b) the altitudes are in H.P.(c) the medians are in G.P. (d) the medians are in A.P.​

Answer»

<P>If p  

1

​  

,p  

2

​  

,p  

3

​  

, are the ALTITUDES from A, B, C respectively,

then Δ=  

2

1

​  

ap  

2

​  

=  

2

1

​  

BP  

2

​  

=  

2

1

​  

CP  

3

​  

 

⇒p  

1

​  

=  

a

​  

,p  

2

​  

=  

b

​  

,p  

3

​  

=  

c

​  

 

By the law of sines

sinA

a

​  

=  

sinB

b

​  

=  

SINC

c

​  

=k(say)

∴=  

ksinA

​  

,p  

2

​  

=  

ksinB

​  

,p  

3

​  

=  

ksinC

​  

 

Now, sinA,sinB,sinC are in A.P.

⇒p  

1

​  

,p  

2

​  

,p  

3

​  

 are in H.P.



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