Let
Δ
A
B
C
be a triangle with vertices
A
,
B
&
C
and
D
,
E
&
F
be the midpoint of sides
A
B
,
B
C
&
C
A
respectively.
If A E = 2 . 5 , C D = 1 3 and B F = 2 7 3 , and P be the image(reflection) of point A about side B C .
Then find the area of the quadrilateral A B P C
Note the given picture is not necessarily correct.
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@Aniket Verma @Purushottam Abhisheikh . Friends you can get this problem very easily . Thanks!
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Ya actually while thinking this question I forgot this formula and proceeded in a bit lengthy way that's why i posted it in level 5. BTW thanks for reminding me about this formula...
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@Vaibhav Prasad how did you do it?
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@Adarsh Kumar – @Adarsh Kumar The area of a triangle = 3 4 times the area of the triangle formed by it's medians.
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@Vaibhav Prasad – Ok!Thanx for replying!Sorry for the late reply,power was out since yesterday 8 30 PM.
@Adarsh Kumar – I used the formula that median of a triangle Δ A B C through its vertex A is equal to 2 b 2 + 2 c 2 − 4 a 2
And formed three equations to find the sides of the triangle...
Quite lengthy ...
Hey! Do u remember posting a question and deleting it soon afterwards ? (It happened a few days ago)
Check out it's disputes .
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Which question? Give me the link...
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Hey!Nihar,did you copy that combi question of yours (that 21,31,41..) from 102 combinatorial problems book?
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@Adarsh Kumar – Yeah! But I didn't "copy" it , I "shared" it.
I did not get the link :/ @Azhaghu Roopesh M
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OK , no problem . Just participate in OPC 3 and I'll get back to u later.
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@A Former Brilliant Member – You are not participating in OPC 3? :( :( :(
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@Nihar Mahajan – IDK , still got some exams to go . The deadline's the 15th right ? I'll see .
If u are on G+, u can catch up with me . I'll be checking thaat out once every day .
Cya!
I used coordinate geometry
Let A(0,a) B(-b,0) & C(c,0)
Then E((c-b)/2,0) D(-b/2,a/2) & F(c/2,a/2)
Using diatance formula we get following equations :
b²+c²-2bc+4a²=25....(1)
4b²+c²+4bc+a²=73....(2)
b²+4c²+4bc+a²=52....(3)
From (2) & (3),
b²-c²=7 &
5b²+5c²+8bc+2a²=125
5(b²+c²-2bc)+18bc+2a²=125
5(25-4a²)+18bc+2a²=125
a²=bc
Plugging this in (1) we get (b+c)²=25 or b+c=5
Hence b-c=7/5
b=16/5, c=9/5 & a=12/5
Area of ABC is 1/2 x (b+c) x a= 6
Area of quad ABPC is 2ABC=12
There is another formula which can be applied to find out the area of a triangle. Let A be = (m1 + m2 + m3)/2, where m1, m2, m3 are the medians of the triangle. Then area of the triangle is given by the following expression:
4/3 x [(A)(A - m1)(A - m2)(A - m3)]^1/2
Sorry guys, still did not learn LaTex :(
I have the best way to learn L A T E X !
Just hover ur cursor over L A T E X codes of others and u'll be a master at it in no time !
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@Azhaghu Roopesh M Yup thats a good idea.. By the way, you are there in the Brilliant Hangouts group right? We shall talk there :)
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Well , I had to leave it due to some reasons , add me back in !
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@A Former Brilliant Member – Okay.. I will do it tomorrow
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Area of triangle A B C where u , v , w are its medians is given by :
3 1 [ 2 ( u 2 v 2 + v 2 w 2 + u 2 w 2 ) − ( u 4 + v 4 + w 4 ) ]
Substituting the values of medians , we get
A ( A B C ) = 6
Since , one of vertices of triangles is refected , it can be proved easily by congruence that :
A ( A B C ) = A ( B P C ) = 6
⇒ A ( A B C P ) = A ( A B C ) + A ( B P C ) = 1 2