## Kweku Group Title write 3(cos225 +isin225) in the form a + ib. one year ago one year ago

1. ZeHanz

225 degrees rings a bell, no?

2. Kweku

it is complex numbers

3. ZeHanz

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. Kweku

you mean right angled triangle?

5. ZeHanz

yeah

6. Kweku

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

7. ZeHanz

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. ZeHanz

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. Kweku

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

10. ZeHanz