1.

Evaluate the following: (i) sin78∘cos18∘−cos78∘sin18∘ (ii) cos47∘cos13∘−sin47∘sin13∘ (iii) sin36∘cos9∘+cos36∘sin9∘ (iv) cos80∘cos20∘+sin18∘sin20∘

Answer»

Evaluate the following:
(i) sin78∘cos18∘−cos78∘sin18∘
(ii) cos47∘cos13∘−sin47∘sin13∘
(iii) sin36∘cos9∘+cos36∘sin9∘
(iv) cos80∘cos20∘+sin18∘sin20∘



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