问下下面的公式都等于神马啊

sin(π+a) = -sinasin(π-a) = sinacos(π+a) = -cosacos(π-a) = -cosatan(π+a) = tanatan(π-a) = -tanasin(π/2+a) = cosasin(π/2-a) = cosacos(π/2+a) = -sinacos(π/2-a) = sinatan(π/2+a) = -cotatan(π/2...