sec 70o sin 20o + cos 20o cosec 70o = ?
(a) 0 (b) 1 (c) -1 (d) 2
sec 70o sin 20o+cos 20o cosec 70o
=sin 20ocos 70o+cos 20osin 70o
=sin (90o−70o)cos 70o+cos (90o−70o)sin 70o
=cos 70ocos 70o+sin 70osin 70o = 1+1 = 2
Hence, the correct choice is (d).