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AQA A Level - Addition Formulae

Trig Addition Formulae & Double Angle Formulae

Prove addition formulae using geometric construction
Visualise sin(2x) Double Angle Formulae
The double angle formulae are useful in solving trigonometric formulae. This display allows you to view formulae relating to sin(ax) with a an adjustable constant.

Initially, a is set to 0 so you can visualise how sin(cx)cos(cx) arises as the product of sin(cx) and cos(cx).

Then, by adjusting a, b and c to make the green and red curves coincide, you can view the double angle formulae, not only for sin(2x), but for other values of a too.
Visualise cos(2x) Double Angle Formulae
The double angle formulae are useful in solving trigonometric formulae. This display allows you to view formulae relating to cos(ax) with a an adjustable constant.

By adjusting a, b, c and d to make the green and red curves coincide, you can view the double angle formulae, for cos(2x) in its different forms.
Visualise sin(x ± a) Addition Formulae
This display allows you to visualise the addition formulae:
sin(x+a)=sin(x)cos(a)+cos(x)sin(a)
sin(xa)=sin(x)cos(a)cos(x)sin(a)
Visualise cos(x ± a) Addition Formulae
This display allows you to visualise the addition formulae:
cos(x+a)=cos(x)cos(a)sin(x)sin(a)
cos(xa)=cos(x)cos(a)+sin(x)sin(a)
Visualise a sin x ± b cos x to sin
This display allows you to visualise the transformations:
asin(x)+bcos(x)=Rsin(x+α)
asin(x)bcos(x)=Rsin(xα)

After adjusting a and b, you can adjust r and α to their derived values to see the two curves coincide.

For a better view, you should use the navigation buttons in the lower right corner to zoom in and out.
Visualise a cos x ± b sin x to cos
This display allows you to visualise the transformations:
acos(x)+bsin(x)=Rcos(xα)
acos(x)bsin(x)=Rcos(x+α)

After adjusting a and b, you can adjust r and α to their derived values to see the two curves coincide.

For a better view, you should use the navigation buttons in the lower right corner to zoom in and out.
sin(x + a) + sin(x - a)
The display shows y=sinx in blue and y=sin(x+a)+sin(xa)
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