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Trignometry

Scorching goIITian

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15 Mar 2007 11:29:40 IST

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806

trignometry......

None

in triangle ABC p.t

sin2A+sin2B+sin2C=4.sinA.sinB.sinC

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vishak p

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15 Mar 2007 11:33:44 IST

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in this quest. sneha first use the formula for sin X + sin Y = 2 sin (X+Y)/2 sin (X-Y)/2 , then substitute the relation A+B+C = pie
it will be a little long, but it will come !
do ask if it doesn't come

sneha kulkarni

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15 Mar 2007 11:43:45 IST

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yes i m trying but tell me....why v should substitute A+B+C=pi......pls tell me

vishak p

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15 Mar 2007 11:45:10 IST

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this is because in a triangle the sum of the angles is = pie !

sneha kulkarni

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15 Mar 2007 11:47:13 IST

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wait.............if we substitue A+B+C=180........

sneha kulkarni

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15 Mar 2007 11:47:57 IST

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yeah...i got it! thanks..........

vishak p

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15 Mar 2007 11:48:49 IST

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always welcome !

supriya

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15 Mar 2007 11:51:07 IST

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combine sin 2B and sin 2B and substitute sin C as (pi - A+B) solving further u'll get it right

ruhi agrawal

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15 Mar 2007 11:54:24 IST

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one more thing.........this relation is quite useful in solving prob. so learn it......u shud know this relation...ok
cheers

sneha kulkarni

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15 Mar 2007 12:03:23 IST

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thanks supriya and ruhi............

goutham harsha (1nkZ)

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15 Mar 2007 15:09:51 IST

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some more imp results.....in a triangle....

1) sin2A+sin2B+sin2C=4 sinAsinBsinC

2)cos2A+cos2B+cos2C= -1-4cosAcosBcosC

3)cosA+cosB+cosC= 1+4

sin(a/2)

sin^2 A=2+2

cosA

cos^2 A=1-2

cosA

6)sin2A+sin2B-sin2C = 4cosAcosBsinC

7)cos2A-cos2B+cos2C= 1-4sinAcosBsinC

8)sinA+sinB-sinC=4sin(A/2)sin(B/2)cos(C/2)

9)cosA+cosB-cosC= -1+4cos(A/2)cos(B/2)sin(C/2)

hope u find these useful.......

Goutham.K

sneha kulkarni

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15 Mar 2007 17:17:11 IST

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hey thanks a lot.............gautham

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