Otdfbt

I have an equation split to multiple lines.
But the last line of the multiline equation contains 2x1 vector with long equations that go out of margin.
How do I further split the equations in the vector so that they do go over margin and look visually pleasing?

beginequation labeleq:7
beginsplit
mathbfy(1)&=tanh(mathbfW^rocdotmathbfh(1)+mathbfW^iocdotmathbfx(1)) \
&=beginbmatrix tanhBig(w^ro_1,1cdotalphacdot tanhbig(w^ir_1,1cdot x_1(1)+w^ir_2,1cdot x_2(1)big) + w^ro_2,1cdot alpha cdot tanhbig(w^ir_1,2cdot x_1(1)+w^ir_2,2 cdot x_2(1)big) + w^io_1,1 cdot x_1(1)+w^io_2,1 cdot x_2(1)Big) \ tanhBig(w^ro_1,2cdot alpha cdot tanhbig(w^ir_1,1cdot x_1(1)+w^ir_2,1cdot x_2(1)big) + w^ro_2,2cdot alpha cdot tanhbig(w^ir_1,2cdot x_1(1)+w^ir_2,2 cdot x_2(1)big) + w^io_1,2cdot x_1(1)+w^io_2,2cdot x_2(1)Big) endbmatrix.
endsplit
endequation

Current output looks like below where good portion of equations go over margin:

Any help will be greatly appreciated

You can break lines within a matrix by useing of multlined from the mathtools package:

documentclassarticle
usepackagegeometry
usepackagemathtools

begindocument
beginequation labeleq:7
beginsplit
mathbfy(1)&=tanh(mathbfW^rocdotmathbfh(1)+mathbfW^iocdotmathbfx(1)) \
 & = beginbmatrix
 beginmultlined
 tanhBigl(w^ro_1,1cdotalphacdot tanhbigl(w^ir_1,1cdot x_1(1) + w^ir_2,1cdot x_2(1)bigr) \[-2ex]
 + w^ro_2,1cdot alpha cdot tanhbigl(w^ir_1,2cdot x_1(1) + w^ir_2,2 cdot x_2(1)bigr) + w^io_1,1 cdot x_1(1)+w^io_2,1 cdot x_2(1)Bigr)
 endmultlined \[4ex]
 %
 beginmultlined
 tanhBigl(w^ro_1,2cdot alpha cdot tanhbigl(w^ir_1,1cdot x_1(1) + w^ir_2,1cdot x_2(1)bigr) \[-2ex]
 + w^ro_2,2cdot alpha cdot tanhbigl(w^ir_1,2cdot x_1(1)+w^ir_2,2 cdot x_2(1)bigr) + w^io_1,2cdot x_1(1)+w^io_2,2cdot x_2(1)Bigr)
 endmultlined
 endbmatrix.
endsplit
endequation
enddocument

note: I try to fix of use Big( and big(. More correct is Bigl( and bigl( and Bigr) and bigr). most of the math operators are defined, so instead ˙tanh you should use tanh which write it correct mathrm font. I also reduce width of cdots enclosing them in curly braces. Do you really need them?

Here there is my proposal:

documentclass[a4paper,12pt]article
usepackagemathtools,amssymb
usepackage[left=1in,right=.3in]geometry

begindocument
beginequation labeleq:7
beginaligned
mathbfy(1)&=tanh(mathbfW^mathrmrocdotmathbfh(1)+mathbfW^mathrmiocdotmathbfx(1)) \
&=beginbmatrix tanhBig((w^mathrmmathrmro_1,1cdotalphacdot tanhmu) + w^mathrmro_2,1cdot alpha cdot tanh lambda + w^mathrmio_1,1 cdot x_1(1)+w^mathrmio_2,1 cdot x_2(1)Big) \ 
tanh Big((w^mathrmro_1,2cdot alpha cdot tanhmu) + w^mathrmro_2,2cdot alpha cdot tanh lambda + w^mathrmio_1,2cdot x_1(1)+w^mathrmio_2,2cdot x_2(1)Big) endbmatrix
endaligned
endequation

where $mu=(w^mathrmir_1,1cdot x_1(1)+w^mathrmir_2,1cdot x_2(1))$ and $lambda=(w^mathrmir_1,2cdot x_1(1)+w^mathrmir_2,2 cdot x_2(1))$
enddocument

I propose this layout, which doesn't require multiline equations inside matrix. Instead, I suppressed the cdots (unnecessary, from my point of view) and used the mmatrix (medium-size matrix) environment from nccmath, and the fleqn environment (same package). This size remains readable, as it is ~80 % of displaystyle.

documentclassarticle
usepackage[showframe]geometry
usepackagemathtools, nccmath

begindocument
vspace*1cm
beginfleqn

beginequation
beginaligned[b] labeleq:7
&mathbfy(1)=tanh(mathbfW^rocdotmathbfh(1)+mathbfW^iocdotmathbfx(1)) = \
 & beginmmatrix beginbmatrix
 tanhBigl(w^ro_1,1 alpha tanhbigl(w^ir_1,1 x_1(1) + w^ir_2,1 x_2(1)bigr)
 + w^ro_2,1 alpha tanhbigl(w^ir_1,2 x_1(1) + w^ir_2,2 x_2(1)bigr) + w^io_1,1 x_1(1)+w^io_2,1 x_2(1)Bigr)
 \
 %
 tanhBigl(w^ro_1,2 alpha tanhbigl(w^ir_1,1 x_1(1) + w^ir_2,1 x_2(1)bigr)
 + w^ro_2,2 alpha tanhbigl(w^ir_1,2 x_1(1)+w^ir_2,2 x_2(1)bigr) + w^io_1,2 x_1(1)+w^io_2,2 x_2(1)Bigr)
 endbmatrix
endmmatrix
endaligned
endequation
endfleqn

enddocument