# Clarification of RSin(x+a), RCos(x+a)

1. Jan 4, 2009

### thomas49th

1. The problem statement, all variables and given/known data
I want to clarify about using RSin(x+a) and RCos(x+a) for aSinbx + cCosbx

If im given y = 3Sin2x + 4cos2x

Can I turn it into RSin(x+a) and RCos(x+a) expressions

HOWEVER

if y = 3Sin2x + 4cos4x Can I turn it into RSin(x+a) and RCos(x+a) expressions?

Thanks :)

2. Jan 4, 2009

### Dick

No, you can't. Try plotting that function. It doesn't look very much like a simple sin or cos graph, does it?

3. Jan 4, 2009

### thomas49th

is that for

if y = 3Sin2x + 4cos4x

"I want to clarify about using RSin(x+a) and RCos(x+a) for aSinbx + cCosbx

If im given y = 3Sin2x + 4cos2x

Can I turn it into RSin(x+a) and RCos(x+a) expressions"

or can you only do one or the other (either RSin(x+a) and RCos(x+a)) and you have to spot each one

Thanks :)

4. Jan 4, 2009

### rock.freak667

For asinbx+cCosbx, once those 'b's are the same, you can turn it into either Rsin(bx+A) or Rcos(bx+A).

5. Jan 5, 2009

### thomas49th

cool cheers :)