Add document of sin and cos
Add document of sin and cos

truongdq/chainer,sinhrks/chainer,niboshi/chainer,keisuke-umezawa/chainer,pfnet/chainer,tigerneil/chainer,sou81821/chainer,Kaisuke5/chainer,hvy/chainer,ktnyt/chainer,cupy/cupy,jnishi/chainer,delta2323/chainer,okuta/chainer,ytoyama/yans_chainer_hackathon,kiyukuta/chainer,woodshop/chainer,chainer/chainer,kashif/chainer,kuwa32/chainer,woodshop/complex-chainer,ktnyt/chainer,wkentaro/chainer,wkentaro/chainer,hvy/chainer,ktnyt/chainer,wkentaro/chainer,chainer/chainer,hvy/chainer,cupy/cupy,cupy/cupy,benob/chainer,cupy/cupy,chainer/chainer,keisuke-umezawa/chainer,jnishi/chainer,jnishi/chainer,umitanuki/chainer,keisuke-umezawa/chainer,anaruse/chainer,minhpqn/chainer,muupan/chainer,niboshi/chainer,okuta/chainer,sinhrks/chainer,yanweifu/chainer,laysakura/chainer,wkentaro/chainer,chainer/chainer,AlpacaDB/chainer,aonotas/chainer,rezoo/chainer,hvy/chainer,tscohen/chainer,benob/chainer,okuta/chainer,t-abe/chainer,muupan/chainer,hidenori-t/chainer,wavelets/chainer,1986ks/chainer,masia02/chainer,tkerola/chainer,keisuke-umezawa/chainer,niboshi/chainer,AlpacaDB/chainer,ysekky/chainer,kikusu/chainer,truongdq/chainer,ktnyt/chainer,kikusu/chainer,t-abe/chainer,niboshi/chainer,jnishi/chainer,ronekko/chainer,ikasumi/chainer,cemoody/chainer,okuta/chainer