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sin and cos driving me nuts!! please help - only a quick question but its annoying!
Hi, I have been trying to do this for AAAAGGGGGEEEEESSSSS and can't get to the right answer...does anyone mind having a look?
Express (3sin2x + cos2x)^2 in the form A sin 4x + B cos 4x + c where A, B and C are integers.
Any help much appreciated - and I will rep you!!
Express (3sin2x + cos2x)^2 in the form A sin 4x + B cos 4x + c where A, B and C are integers.
Any help much appreciated - and I will rep you!!
Reply 1
which unit of maths is this for??
Reply 2
Raman87
Hi, I have been trying to do this for AAAAGGGGGEEEEESSSSS and can't get to the right answer...does anyone mind having a look?
Express (3sin2x + cos2x)^2 in the form A sin 4x + B cos 4x + c where A, B and C are integers.
Any help much appreciated - and I will rep you!!
Express (3sin2x + cos2x)^2 in the form A sin 4x + B cos 4x + c where A, B and C are integers.
Any help much appreciated - and I will rep you!!
9sin^2(2x)+6sin2xcos2x+cos^2(2x)
8sin^2(2x)+sin^2(2x)+3sin(4x)+cos^2(2x)..........sin(4x)=2cos(2x)sin(2x)
4(1-cos(4x)+3sin(4x)+1.............cos(4x)=1-2sin^2(2x)=> 2sin^2(2x)=(1-cos(4x))
3sin(4x)-4cos(4x)+5
Reply 3
Raman87
OP
9sin^2(2x)+6sin2xcos2x+cos^2(2x)
8sin^2(2x)+sin^2(2x)+3sin(4x)+cos^2(2x) I don't understand how u've got from here to the next bit..
[cos(4x)=cos(2x+2x)=cos^2(2x)-sin^(2x)=1-2sin^2(2x)
so 8sin^2(2x)=4(1-cos(4x))
giving us
4-4cos(4x)+3sin(4x)+1
=3sin(4x)-4cos(4x)+5
8sin^2(2x)+sin^2(2x)+3sin(4x)+cos^2(2x) I don't understand how u've got from here to the next bit..
[cos(4x)=cos(2x+2x)=cos^2(2x)-sin^(2x)=1-2sin^2(2x)
so 8sin^2(2x)=4(1-cos(4x))
giving us
4-4cos(4x)+3sin(4x)+1
=3sin(4x)-4cos(4x)+5
Reply 4
Raman87
9sin^2(2x)+6sin2xcos2x+cos^2(2x)
8sin^2(2x)+sin^2(2x)+3sin(4x)+cos^2(2x) I don't understand how u've got from here to the next bit..
[cos(4x)=cos(2x+2x)=cos^2(2x)-sin^(2x)=1-2sin^2(2x)
so 8sin^2(2x)=4(1-cos(4x))
giving us
4-4cos(4x)+3sin(4x)+1
=3sin(4x)-4cos(4x)+5
8sin^2(2x)+sin^2(2x)+3sin(4x)+cos^2(2x) I don't understand how u've got from here to the next bit..
[cos(4x)=cos(2x+2x)=cos^2(2x)-sin^(2x)=1-2sin^2(2x)
so 8sin^2(2x)=4(1-cos(4x))
giving us
4-4cos(4x)+3sin(4x)+1
=3sin(4x)-4cos(4x)+5
ive edited my post, hopefully it makes more sense
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