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Maths
A Level

differentiate x^2 + y^3 + xy respect to x

2x + 3y2 * dy/dx + x * dy/dx +y 

XJ
Answered by Xianming J. Maths tutor
3162 Views

dx/dt=-5x/2 t>=0 when x=60 t=0

dx/dt=-5x/2 Int(x, dx)=Int(-5/2, dt) ln(x)=-5t/2+c x=60 when t=0 ln(60)=c ln(x)=ln(60)-5t/2 x=eln(60)-5t/2 x=60/e5t/2

FD
Answered by Felix D. Maths tutor
4562 Views

Given that sin(x)^2 + cos(x)^2 = 1, show that sec(x)^2 - tan(x)^2 = 1 (2 marks). Hence solve for x: tan(x)^2 + cos(x) = 1, x ≠ (2n + 1)π and -2π < x =< 2π(3 marks)

sin(x)2 + cos(x)2 = 1

Dividing by cos(x)2 gives:

tan(x)2 + 1 = sec(x)2 

Which rearranges as:

sec(x)2 - tan(x)<...

AR
Answered by Alistair R. Maths tutor
3496 Views

Solve for 0 =< x =< 360 16/(cos(x+25)+1) = 10, give answers to 2 d.p.

Rearrange to get cos(x+25) = 0.6

Use inverse cosine to get (x+25) = -53.13... 53.13... 306.86... 413.13...

Isolate x to get x = -78.13... 28.13... 281.86... 388.13...

Apply the limits...

BW
Answered by Barnaby W. Maths tutor
3934 Views

if f(x) = 7x-1 and g(x) = 4/(x-2), solve fg(x) = x

fg(x) = 7(4/x-2) -1 = x

28/(x-2) - 1 = x

28/(x-2) = x +1

28 = (x+1)(x-2)

28 = x2 - x - 2

0 = x2 - x - 30

0 = (x-6)(x+5)   x=6 x=-5

SW
Answered by Sophie W. Maths tutor
15005 Views

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