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Maths
A Level

Express 5cosx - 3sinx in the form Rcos(x+a).

cos(x+a)=cosxcosa-sinxsina so cosa=5 sina=3 which means tana=3/5 a=0.54 RADIANS R=sqrt(52+32). =sqrt(34) so sqrt(34)cos(x+0.54)

EH
Answered by Elizabeth H. Maths tutor
15756 Views

Differentiate sin(5x) and 3cos(x) and 3tan(5x)

sin cos -sin -cos (down is differentiate and up is integrate) so, y = sin5x  dy/dx = 5cos5x y=3cox      dy/dx = -3sinx y=3tan5x     dy/dx = 15sec2(5x) (remember sec(x) is the reciprocal of cos(...

AC
Answered by Abi C. Maths tutor
4776 Views

Find where the curve 2x^2 + xy + y^2 = 14 has stationary points

d/dx (xy) = x dy/dx + y 

d/dx (y^2) = 2y dy/dx [This is from the chain rule]

So, d/dx (2x^2 + xy + y^2 = 14) 

=> 4x + x dy/dx + y + 2y dy/dx = 0

set dy/dx = 0 as stationary ...

MH
Answered by Matthew H. Maths tutor
8626 Views

Using complex numbers, derive the trigonometric identities for cos(2θ) and sin(2θ).

When dealing with complex numbers and trigonometric functions, always turn to DeMoivre's Theorem that states [cos(θ)+isin(θ)]n = [cos(nθ)+isin(nθ)]. If we set n=2, the we see a combina...

TK
Answered by Thomas K. Maths tutor
8537 Views

Integrate (x+3)^(1/2) .dx

[whiteboard feature does not seam to be working here] 

Here we need to make a U sibstitution. So we take (x+3) and make this equal U so we now have the integral of u^1/2   . dx

In order to s...

CZ
Answered by Callum Z. Maths tutor
4413 Views

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