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# Rsin(pheta-alpha) help watch

1. Express 8sin.pheta - 6cos.pheta in the form Rsin(pheta - alpha) where R>0 and 0<alpha<90

I get r=2[sqroot]21
But according to the mark scheme, r=10

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2. (Original post by SDavis123)
Express 8sin.pheta - 6cos.pheta in the form Rsin(pheta - alpha) where R>0 and 0<alpha<90

I get r=2[sqroot]21
But according to the mark scheme, r=10

Posted from TSR Mobile

I get R to equal 10...

What did you do to get 2sqrt21?
3. (Original post by usycool1)
I get R to equal 10...

What did you do to get 2sqrt21?

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4. You've made a basic arithmetic error at the end.

5. (Original post by usycool1)
You've made a basic arithmetic error at the end.

Ahhh ok lol, thanks

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