Here's the question you clicked on:
Kweku
write 3(cos225 +isin225) in the form a + ib.
225 degrees rings a bell, no?
Not yet ;) I meant that sin225 and cos225 are supposed to be well-known numbers: they have to do with the 45-45-90 degree triangle, with sides a, a and a√2. Does that ring a bell? See image. Both sin225 and cos225 are: \[-\frac{ 1 }{ 2 }\sqrt{2}\]
you mean right angled triangle?
so you mean the angles should be in the first quadrant?
No, 225 is in the third quadrant. I only meant that in the 3rd quadrant you get the same values (just negative) as in the triangle with 45-45-90 degrees.
Therefore you now have \[3(-\frac{ 1 }{ 2 }\sqrt2+i \cdot -\frac{ 1 }{ 2 }\sqrt 2)\]And if you work out the brackets you're done.
Yeah I get you but that does not make any change.
Is your problem solved then?