f(x)=2sinx=8cos(1/2)x???

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- Sep 4th 2008, 10:38 PMNotEinsteinhow do i evaluate...
f(x)=2sinx=8cos(1/2)x???

- Sep 4th 2008, 10:43 PMMatt Westwood
By plugging in the values of x you're interested in, surely?

- Sep 4th 2008, 10:45 PMNotEinstein
at x=pi/6

- Sep 4th 2008, 10:55 PMMatt Westwood
pi/6 is 30 degrees.

So it's 2 times sin (30 degrees) minus 8 times cos (15 degrees).

But I'm assuming a level of mathematics which is higher than just looking stuff up in tables yeah? In which case you might want to try the half-angle formulae to express that cos in terms of things which have pi/6's in so you can use the standard values of sin and cos of pi/6. Have fun.