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Question
Evaluate:
`cos70^circ/(sin20^circ) + cos59^circ/(sin31^circ) - 8 sin^2 30^circ`
Solution
`cos70^circ/(sin20^circ) + cos59^circ/(sin31^circ) - 8 sin^2 30^circ`
= `cos(90^circ - 20^circ)/(sin20^circ) + cos(90^circ - 31^circ)/(sin31^circ) - 8(1/2)^2`
= `sin20^circ/(sin20^circ) + sin31^circ/(sin31^circ) - 2`
= 1 + 1 – 2
= 0
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