Here,
,
,
,
,
,
and
.
is the incenter of the triangle
. If
is the distance of
from
then we can write
. What is the value of
(in meter) ?
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Our first target is to find out another side of △ P Q R
In △ A B P ,
∠ A P B = 1 8 0 ∘ − ( 3 0 ∘ + 6 0 ∘ ) = 9 0 ∘
Hence, cos 3 0 ∘ = 2 0 0 B P
B P = 2 0 0 cos 3 0 ∘ = 1 7 3 . 2 m
Again, In △ A B Q ,
Hence, sin 4 6 ∘ B Q = sin 6 7 ∘ 2 0 0
B Q = 1 5 6 . 3 m
Then in △ P B Q ,the cosine rule gives,
P Q 2 = B P 2 + B Q 2 − 2 ∗ B P ∗ B Q cos 9 7 ∘ = ( 1 7 3 . 2 ) 2 + ( 1 5 6 . 3 ) 2 − 2 ( 1 7 3 . 2 ) ( 1 5 6 . 3 ) ( − . 1 2 1 9 )
Hence, P Q = 2 4 7 m
Now,In △ P Q R ,
sin 8 0 . 6 ∘ 2 6 6 . 3 6 = sin P R Q 2 4 7
or, sin P Q R = . 9 1 4 8 6 4 5 5
or, ∠ P Q R = sin − 1 ( . 9 1 4 8 6 4 5 5 )
so, ∠ P Q R = 6 6 . 1 9 ∘
Again △ P Q R ,
∠ R P Q = 1 8 0 ∘ − ( 8 0 . 6 ∘ + 6 6 . 1 9 ∘ )
so, ∠ R P Q = 3 3 . 2 1 ∘
Now,In △ P Q R ,
sin 8 0 . 6 ∘ 2 6 6 . 3 6 = sin 3 3 . 2 1 ∘ R Q
so, R Q = 1 4 7 . 8 7
The area of the △ P Q R = 1 / 2 ∗ r ∗ p ∗ sin P Q R
= 1 / 2 ∗ 2 4 7 ∗ 1 4 7 . 8 7 ∗ sin 8 0 . 6 ∘
= 1 8 0 1 6 . 7 3
Let x is the distance of O from p or q or r
Area of △ P O Q = 1 / 2 ∗ r ∗ x
Area of △ R O P = 1 / 2 ∗ q ∗ x
Area of △ R O Q = 1 / 2 ∗ p ∗ x
Thus the total area of △ P Q R = 1 / 2 ∗ x ( p + q + r ) = 3 0 0 . 6 1 5 ∗ x
But this area is 1 8 0 1 6 . 7 3 . Herce, the area of O from R Q , x = 3 0 0 . 6 1 5 1 8 0 1 6 . 7 3 = 5 4 . 5
We can write a < 5 4 . 5 < a + 1 5 4 < 5 4 . 5 < 5 4 + 1 or 5 4 < 5 4 . 5 < 5 5
SO, a = 5 4