Top answers
Maths
A Level
Using the identity cos(A+B)= cosAcosB-sinAsinB, prove that cos2A=1-2sin^2A.
Use cos(A+B)=cosAcosB-sinAsinB and let A=B so cos(A+A)=cosAcosA-sinAsinA this means cos(2A)=cos2A-sin2A and since cos2A+sin2A=1, cos2A=1-sin2
A curve has the equation: x^3 - x - y^3 - 20 = 0. Find dy/dx in terms of x and y.
x3 - x - y3 - 20 = 0 Find dy/dx. Differentiate with respect to x.
3x2 - 1 - 3y2(dy/dx) = 0Therefore: dy/dx = (3x
