Question

how to solve for cosh(3i)?

Answer 1

coshx = (e^x + e^-x)/2
so just substitute x=3i

Answer 2

oh thanks! :)

Answer 3

can't solve it using a sci. calculator tho..

Answer 4

no you can't! need to convert e^3i to x+yi & e^-3i to u+vi

Answer 5

cosh(i*x) = cos(x)

Answer 6

using euler's formula

Answer 7

convert? isn't 3i already in rectangular form? :)

Answer 8

no. e^3i is in polar form. but Dan has given it away

Answer 9

\[\cosh(i*x) = \frac{ 1 }{ 2 }[e ^{ix} + e ^{-ix}] = \cos(x)\]

Answer 10

e^3i = cos3 + isin3 and e^-3i = cos(-3) + isin(-3)
so (e^3i + e^-3i)/2 = cos3

Answer 11

all u have to know is euler's formula

Answer 12

now you can use a calculator :)

Answer 13

also you can use the fact that cos(-x) = cos x