LHs= `(sinalpha + cosalpha)(tanalpha + cotalpha)`
`=(sinalpha + cosalpha)((sin^(2)alpha + cos^(2)alpha)/(sinalpha. Cosalpha))`
`=(sinalpha + cosalpha). (1/(sinalpha.cosalpha))` `[therefore sin^(2)theta + cos^(2)theta=1]`
`=1/(cosalpha)+ 1/(sinalpha)` `[therefore sectheta = 1/costheta` and `cosectheta=1/sintheta]`
`secalpha + cosalpha= RHS`
