Help urgent maths

Alevelhelp.1

15

Help I don’t get how they did this question which double angle formula was used?

(edited 10 months ago)

Reply 1

mqb2766

21

The first one is
sin(2x) = 2sin(x)cos(x)
and square both sides. Then they used another double angle for
sin^2(2x)
to get ~cos(4x). As per the previous post, you should expect that the original integrand will transform into trig(4x) as its a product of 4 trig terms. They do it in two steps.

(edited 10 months ago)

Reply 2

Alevelhelp.1

OP

15

Original post by mqb2766

The first one is
sin(2x) = 2sin(x)cos(x)
and square both sides. Then they used another double angle for
sin^2(2x)
to get ~cos(4x). As per the previous post, you should expect that the original integrand will transform into trig(4x) as its a product of 4 trig terms. They do it in two steps.

This is so hard… I forgot everything and my real a level exam is on Monday

Reply 3

mqb2766

21

For the double angles, it should be relatively straight forward as when you have a product of two trig terms, so sin*cos or sin^2 or cos^2, it pretty much maps directly onto a single trig function which has an argument which is a double angle. Its just the angle addition identity / geometrry proofs. Triple angles are then given by angle addition identity for (2x+x) and you know the double angle identities so ..

Reply 4

Alevelhelp.1

OP

15

Original post by mqb2766

For the double angles, it should be relatively straight forward as when you have a product of two trig terms, so sin*cos or sin^2 or cos^2, it pretty much maps directly onto a single trig function which has an argument which is a double angle. Its just the angle addition identity / geometrry proofs. Triple angles are then given by angle addition identity for (2x+x) and you know the double angle identities so ..