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Stratified sampling is a technique used in some instances to generate a 'fairer' sample than standard random sampling. Wherein a population is divided into subgroups called 'strata'. These strata are usua...

Let a=60 and b=300.

Then cos(a)=cos(60)=0.5 and cos(b)=cos(300)=0.5, therefore cos(a)=cos(b).

Then sin(a)=sin(60)=sqrt(3)/2 and sin(b)=sin(300)=-sqrt(3)/2, therefore sin(a)=sin(b) is incorre...

dy/dx=2x + 2

Turning point is where dy/dx=0, so when x = -1

When x=-1, y=0.

d^2y/dx^2=2 > 0 therefore minimum.

3e^3x + (9x)e^3x This is a good question because it involves the use of both the chain and product rules of differentiation, as well as the differential of e (all of which occur frequently in Maths A-leve...

Let a be the first term

Let d be the common difference

a + d = 7

S₄ = 4/2 (2a +3d) = 12

Simultaneous equation:

a+d =7 // x 6
4a +6d = 12

Differen...