Hi, I am revising on Trig at the moment.

Would you say;

R sin (x+36.9) = R cos (x-53.1)

I have just transformed these equations from 3 cos x - 4 sin x using the alpha method.

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- Feb 8th 2011, 03:11 PMGooglIs this true?
Hi, I am revising on Trig at the moment.

Would you say;

R sin (x+36.9) = R cos (x-53.1)

I have just transformed these equations from 3 cos x - 4 sin x using the alpha method. - Feb 8th 2011, 03:17 PMdwsmith
- Feb 8th 2011, 03:22 PMGoogl
- Feb 8th 2011, 03:24 PMdwsmith
- Feb 8th 2011, 03:30 PMGoogl
Try to write as;

and

[alpha] is the alpha symbol

That - Feb 8th 2011, 07:08 PMSoroban
Hello, Googl!

Quote:

We have: .

Multiply by

. . .[1]

Let be an acute angle is a 3-4-5 right triangle.

Code:

*

/|

/ |

5 / |4

/ |

/α |

*-----*

3

And we have: .

Substitute into [1]:

. .

Therefore: .

. . where

- Feb 8th 2011, 11:32 PMGoogl
I forgot to give you the R values sorry. R is 5 in my original post and it's similar to what you have here.

Would you say;

Try to change it into the form;

R sin (x + [alpha])

alpha is the alpha symbol. - Feb 9th 2011, 04:08 AMHallsofIvy
36.9+ 53.1= 90.0 so if x is in

**degrees**, yes, that is true. If we let y= x+ 36.9, then x- 53.1= y- 36.9- 53.1= y- 90.

But cos(y- 90)= cos(90- y) (since cosine is an even function) and it is always true that sin(y)= cos(90- y).

Quote:

I have just transformed these equations from 3 cos x - 4 sin x using the alpha method.

- Feb 9th 2011, 02:19 PMGoogl
Thanks.