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Trignometry

Hot goIITian

 Joined: 20 Oct 2008 Post: 194
1 Mar 2009 19:53:04 IST
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cos(A+B) + sin(A-B) = 2sin (45+A)cos(45+B)
Engineering Entrance , JEE Main , JEE Main & Advanced , Mathematics , Trigonometry

cos(A+B) + sin(A-B) = 2sin (45+A)cos(45+B)

Blazing goIITian

Joined: 1 Apr 2007
Posts: 4025
2 Mar 2009 00:32:39 IST
1 people liked this

apply the formula of :

2 sin A . cos B in RHS.......

Blazing goIITian

Joined: 7 May 2007
Posts: 1724
11 Mar 2009 08:22:10 IST
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APPLY THE FORMULA 2 SINA COS B =SIN(A+B) + SIN(A-B)  IN RHS.

=>RHS=SIN(90+A+B) +SIN(A-B)

=COS(A+B) + SIN(A-B) =LHS

Cool goIITian

Joined: 10 Mar 2009
Posts: 45
11 Mar 2009 09:41:49 IST
1 people liked this

cos(A+B)=sin(90-A-B)

sin(90-A-B) + sin(A-B) = 2sin(45+A)cos(45+B)

we know that sin(x) + sin(y)=2sin([x+y]/2)cos([x-y]/2)

so we get that

sin(90-A-B) + sin(A-B)=2sin(45-B)cos(45-A)

but we know that sin(45-B)=cos(90-(45-b))=cos(45+B) and cos(45-A)=sin(90-(45-A))=sin(45+A)

hence we get that

cos(A+B) + sin(A-B) = 2sin(45+A)cos(45+B)

do rate me.........

Cool goIITian

Joined: 10 Mar 2009
Posts: 45
11 Mar 2009 15:26:24 IST
0 people liked this

i have given each and every step perfectly....

wat else do u want..... plz give me full ratings.....

Blazing goIITian

Joined: 7 May 2007
Posts: 1724
18 Mar 2009 22:50:19 IST
0 people liked this

APPLY THE FORMULA 2 SINA COS B =SIN(A+B) + SIN(A-B)  IN RHS.

=>RHS=SIN(90+A+B) +SIN(A-B)

=COS(A+B) + SIN(A-B) =LHS

PLSSSSSSSSSSSS      RATEEEEEEEEEEEEEEE

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