Why is it that cos(x) * cos(x) = cos^2(x) as opposed to cos(x)^2 ?

Is this something to do with the trig identities? What identities are useful to know off by heart?

Thanks

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- Jun 14th 2011, 07:48 AM #1

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- Jun 14th 2011, 08:08 AM #2
## Re: cos(x) * cos(x)

It's a convention and, as will all conventions, it eliminates ambiguity. Nothing to do with identities, they still hold.

Is equal to (a lot of brackets, especially if you have lots of trig functions) or ?

IMO there are only four trig identities you need to know

You can derive all your other identities from these

- Jun 14th 2011, 08:23 AM #3

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## Re: cos(x) * cos(x)

Although it is not a good notation, many people don't write the ( ) in sin(x), just sin x. That would make it too easy to confuse (sin(x))^2 with sin(x^2). Of course, you

**can**write (sin(x))^2 (with the parentheses) but it is simpler to write sin^2(x). In general, if f(x) is a function of x, f^2(x) means f(x)*f(x)= (f(x))^2.

- Jun 14th 2011, 08:51 AM #4

- Jun 15th 2011, 12:06 AM #5

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- Jun 15th 2011, 06:13 AM #6

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