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C3 help... watch

1. Hey, I got the markschemes to these, but still don't understand how they got the answer, could some1 explain?
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2. f(x)=2x-1/x-1
y=2x-1/x-1
y(x-1)=2x-1
yx-y=2x-1
(y-2)x=y-1
x=y-1/y-2
F(x)^-1= x-1/x-2
3. sin2x+sin2y= 2sin[(2x+2y)/2]cos[(2x-2y)/2]=2sin(x+y)cos(x-y)
cos2x+cos2y=2cos[(2x+2y)/2]cos[(2x-2y)/2]=2cos(x+y)cos(x-y)
thus,
(sin2x+sin2y)/(cos2x+cos2y)=sin(x+y)/cos(x+y)= tan(x+y)
4. (Original post by he1c14h10)
f(x)=2x-1/x-1
y=2x-1/x-1
y(x-1)=2x-1
yx-y=2x-1
(y-2)x=y-1
x=y-1/y-2
F(x)^-1= x-1/x-2
U lost me there
5. tan 52.5= tan(30+22.5)= (sin60+sin45)/(cos60+cos45)=(root3/2+ root2/2)/(1/2+root2/2)=(root3+root2)/(1+root2)=-(root3+root2)(1-root2)=-root3+root6+root2-2
6. (Original post by [email protected])
U lost me there
sorry..

yx-y=2x-1

-> yx-2x=y-1

->(y-2)x=y-1

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