A-Level Maths: E6-09 Equivalent Forms: Writing acosθ + bsinθ in the form rcos(θ±α) or rsin(θ±α)

[itsshanababyy]

Got a chest infection and have missed 2 weeks off of school and this guy is SAVING mee thank you :)))

[nancykaguima]

I was about to cry about this before I saw this video. Thanks for explaining it in such an easy way

[bakhtavartahir]

You are awesome- thank you for helping me study during the pandemic! Your videos have helped me a lot!

[bensmith]

I'm going through the AQA year 2 Trigonometry for some revision and can't quite get my head around the factor formulas. Are these in the exam and would you be able to make a few videos on going through some questions using them?

[ItzSlashyyy]

Ty, thought this was the hardest topic we have done so far until watching this video

[kakashi]

those 2 equations you derived, r = root (a^2 + b^2) (where a & b are positive lengths) and alpha = tan^-1(a/b) again where u take the magnitude of a & b always seem to work (I've tried them for a few qs). Can u just use these in the exam or will u not get method/working out marks

[misan]

How would you use this to find maximum and minimum with the x value for said minimum and maximum?

[digitella-]

Great video! but can you make a video with how to solve 2sin2x+3cos2x=1 in the range of 0=<x=<360

[l.o]

Does alpha have to be positive for this to work? I did a question using a negative alpha but I ended up with the wrong sign at the end?

[mrgab]

Instead can you write sin(θ+ α) = r(asinθ/r + bcosθ/r) (as if the r's cancel out)


so that you can can say a/r = cos α and b/r = sin α


and solve for 'r' or 'α'

Can you do this to save time on expanding brackets and making silly mistakes when comparing coefficients?
will you get full marks for this?

My exam board is OCR MEI BTW :)