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# Osborn's Rule watch

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1. I have a question about Osborn's rule.

"Use Osborn's rule to convert the following expression, which is given in hyperbolic terms, into an expression containing corresponding trigonometric terms: 4sinh(x+(pi/6))=5.464102cosh(x)"

I don't know what I need to do.
2. (Original post by mickturner)
I have a question about Osborn's rule.

"Use Osborn's rule to convert the following expression, which is given in hyperbolic terms, into an expression containing corresponding trigonometric terms: 4sinh(x+(pi/6))=5.464102cosh(x)"

I don't know what I need to do.
Simple, just use the identity for sinh(a+b) on the LHS and then re-arrange the equation. Whenever you see a sin^2 term it's negative in its hyperbolic equivalent as opposed to positive.

For example usually (using one of the basic trig identities):

but in hyperbolics it's:

I hope that helps
3. (Original post by a10)
Simple, just use the identity for sinh(a+b) on the LHS and then re-arrange the equation. Whenever you see a sin^2 term it's negative in its hyperbolic equivalent as opposed to positive.

For example usually (using one of the basic trig identities):

but in hyperbolics it's:

I hope that helps

So would my answer look a bit like this?

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