## anonymous 3 years ago write 3(cos225 +isin225) in the form a + ib.

1. anonymous

225 degrees rings a bell, no?

2. anonymous

it is complex numbers

3. anonymous

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: $-\frac{ 1 }{ 2 }\sqrt{2}$

4. anonymous

you mean right angled triangle?

5. anonymous

yeah

6. anonymous

so you mean the angles should be in the first quadrant?

7. anonymous

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.

8. anonymous

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.

9. anonymous

Yeah I get you but that does not make any change.

10. anonymous