Q39 of 268 Page 4

Find the value off the following:

sec 70°. sin 20° - cos 20°. cosec 70°

sec 70° sin 20° - cos 20° cosec 70°

= cosec (90°-70°) cos (90° - 20°)- cos 20° cosec 70°


[∵ sec θ = cosec (90° - θ) and Sin θ = cos (90° - θ)]


= cosec 70° cos 20° - cos 20° cosec 70°


=0


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