## anonymous 3 years ago find all solutions for cos z = 2, z=x+iy?

1. anonymous

2-iy = x

2. anonymous

2-x/i = y

3. anonymous

2-x/y = i

4. anonymous

you need to start with $\frac{1}{2}(e^{iz}+e^{-iz})=2$

5. anonymous

then to $e^{iz}+e^{-iz}=4$ and then $e^{2iz}+4e^{iz}+1=0$ solve the quadratic equation in $$e^{iz}$$

6. anonymous

typo i mean $e^{2iz}-4e^{iz}+1=0$

7. anonymous

ohh. ic. thx.

8. anonymous

yw

9. anonymous

cos never be 2 in maths

10. anonymous

-1<cosx<1