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Mathematics 20 Online
OpenStudy (anonymous):

Hyperbolic functions..

ganeshie8 (ganeshie8):

\(\large y= c_1 \sinh (kx) + c_2 \cosh (kx) \)

ganeshie8 (ganeshie8):

take the derivative, wat do u get ?

ganeshie8 (ganeshie8):

use below : (sinhx)' = coshx (coshx)' = sinhx

OpenStudy (anonymous):

okay, the derivative of sinh is cosh and derivative of cosh is -sinh..

ganeshie8 (ganeshie8):

derivative of cosh is just sinh

ganeshie8 (ganeshie8):

there is no negative sign

ganeshie8 (ganeshie8):

\(\large y= c_1 \sinh (kx) + c_2 \cosh (kx)\) take derivative \(\large y'= c_1 \cosh (kx)(k) + c_2 \sinh (kx)(k)\) \(\large ~~~= c_1k \cosh (kx) + c_2k \sinh (kx)\)

ganeshie8 (ganeshie8):

take derivative again

ganeshie8 (ganeshie8):

you wud get : \(\large y'= c_1k \cosh (kx) + c_2k \sinh (kx)\) \(\large y''= c_1k \sinh (kx)(k) + c_2k \cosh (kx)(k)\) \(\large ~~~~= c_1k^2 \sinh (kx) + c_2k^2 \cosh (kx)\) \(\large ~~~~= k^2\left(c_1\sinh (kx) + c_2 \cosh (kx)\right)\)

ganeshie8 (ganeshie8):

the thing inside parenthesis should look familiar ?b

OpenStudy (anonymous):

well, i thought the derivative of cos is -sin

OpenStudy (anonymous):

im sorry but imma little bit confused.. but.. how do i take the derivative after this? im sorry

ganeshie8 (ganeshie8):

derivative of \(\cos(x)\) is \(-\sin (x)\) derivative of \(\cosh(x)\) is \(\sinh (x)\)

OpenStudy (anonymous):

yes.. they're correct and what's after this? =)

terenzreignz (terenzreignz):

What's \(\large k^2 y =\color{red}?\)

ganeshie8 (ganeshie8):

stare at last line

ganeshie8 (ganeshie8):

\(\large ~~~~= k^2\left(c_1\sinh (kx) + c_2 \cosh (kx)\right)\)

ganeshie8 (ganeshie8):

the thing inside parenthesis is exactly same as ur given function \(y\) right ?

ganeshie8 (ganeshie8):

we're done actually :)

ganeshie8 (ganeshie8):

just replace the entire thing inside parenthesis wid "y"

ganeshie8 (ganeshie8):

\(\large y'' ~~~~= k^2\left(c_1\sinh (kx) + c_2 \cosh (kx)\right)\) \(\large y'' ~~~~= k^2\left(y\right)\)

ganeshie8 (ganeshie8):

slap that right hand side stuff to left side

ganeshie8 (ganeshie8):

\(\large y'' - k^2\left(y\right) = 0\)

OpenStudy (anonymous):

Thank you so much!!!!!!!!!!!! =)

ganeshie8 (ganeshie8):

let me knw if smthng doesnt make sense :)

ganeshie8 (ganeshie8):

u wlc ! :)

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