CIE A Level Maths: Pure 3复习笔记3.2.3 R addition formulae Rcos Rsin etc

R addition formulae Rcos Rsin etc

How can I simplify expressions like sin ± b cos x  or cos ± b sin x?

  • If a and b are positive constants, then
    • sin bcos x can be rewritten as sin (α)
    • sin bcos x can be rewritten as sin (α)
    • cos bsin x can be rewritten as cos (α)
    • cos bsin x can be rewritten as cos (α)
  • In all four cases > 0 and 0 < α < 90°, with:

Rcos(x+a) Illustr 1, A Level & AS Maths: Pure revision notes

  • To rewrite the expression use the appropriate compound angle formula and equate coefficients

Rcos(x+a) Illustr 2, A Level & AS Maths: Pure revision notes

Exam Tip

  • There is more than one way to rewrite a given expression, and the question in the exam will tell you which form to use.

Worked Example

Rcos(x+a) Example, A Level & AS Level Pure Maths Revision Notes

 

 

 

 

 

 

 

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