sin(a-b)-cosasin(-b)=sinacosb-sinbcosa+cosasinb=sinacosb
cos(a+b)+sin(-a)sin(-b)=cos(a+b)+siasinb=cosacosb-sinasinb+sinasinb=cosacosb
sin(a-b)-cosasin(-b)=sinacosb-sinbcosa+cosasinb=sinacosb
cos(a+b)+sin(-a)sin(-b)=cos(a+b)+siasinb=cosacosb-sinasinb+sinasinb=cosacosb