Visitor

2016-04-30 07:11:45

#1

Hi,

I need some help with this exercicse:

sin^{2} (a + b) = cos^{2}a + cos^{2}b - 2cos(a)cos(b)cos(a + b)

I have to show that this is true.

I need some help with this exercicse:

sin

I have to show that this is true.

Member

2016-04-30 07:16:13

#2

So, you have this

sin^{2} (a + b) = cos^{2}a + cos^{2}b - 2cos(a)cos(b)cos(a + b)

We have to use this formula

sin

We have to use this formula

I'm gonna start with the member from the right. So though, we have:

And then we know the formula: sin^{2} a + cos^{2}a = 1 => cos^{2} a = 1 - sin^{2}a

and we have

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