1.

` (cos 70^@)/(sin 20^@) + (cos 59^@)/(sin 31^@) = 8 sin^2 30^@`

Answer» Here, we will use `sin(90-theta) = costheta and cos(90-theta) = sintheta`
` L.H.S. = (cos70^@/sin20^@) + (cos59^@/sin31^@)`
`= (cos(90-20)^@/sin20^@) + (cos(90-31)^@/sin31^@)`
`= (sin20^@/sin20^@) + (sin31^@/sin31^@)`
`=1+1 = 2`
`R.H.S. = 8sin^2 30^@ = 8(1/2)^2 = 2`
`:. L.H.S = R.H.S.`


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