A-level Physics waves question

For AQA do we need to know the derivation of the formula sini1/sini2 = c1/c2? It isn't very clear if we need to know it

Are you talking about the trigonometry identity:

\frac{\sin A}{a} = \frac{\sin B}{b}

Not sure whether this is the "latest" spec, but I can't see anything specific mentioned in Section 6.5, however it is rather open ended...:
https://filestore.aqa.org.uk/resources/physics/specifications/AQA-7407-7408-SP-2015.PDF

If I were you, if it isn't provided in the formula sheet, then just memorise it unless your teacher says otherwise.

OP

Are you talking about the trigonometry identity:

\frac{\sin A}{a} = \frac{\sin B}{b}

Not sure whether this is the "latest" spec, but I can't see anything specific mentioned in Section 6.5, however it is rather open ended...:
https://filestore.aqa.org.uk/resources/physics/specifications/AQA-7407-7408-SP-2015.PDF

If I were you, if it isn't provided in the formula sheet, then just memorise it unless your teacher says otherwise.

ok thankss xx