Question

Find the value of cos 570° sin 510° + sin (-330°) cos (-390°).​

Answer 1

Answer:

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Answer 2

Question :

Find the value of cos 570° sin 510° + sin (-330°) cos (-390°)

Solution :

$\sf \small cos(360 \degree + 210\degree)sin(360\degree + 150\degree) - sin330\degree cos390\degree = 0$

$\sf \small \rightarrow cos210\degree sin150\degree - sin(360\degree - 30\degree) cos(360\degree + 130\degree) = 0$

$\sf \small \rightarrow cos(180\degree + 30\degree)sin(180\degree - 30\degree) - ( - sin30\degree)cos30\degree$

$\sf \small \rightarrow - cos \: 30\degree \: sin \: 30\degree + sin 30\degree \: cos \: 30\degree = 0$

$\sf \small \rightarrow 0 = 0$

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