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Question
Find the value of the following:
sin (-105°)
Solution
sin (-105°) = -sin (105°) (∵ sin (-θ) = – sin θ)
= -[sin(60° + 45°)]
= -[sin 60° cos 45° + cos 60° sin 45°]
`= -[sqrt3/2 xx 1/sqrt2 + 1/2 xx 1/sqrt2]`
`= - [sqrt3/(2sqrt2) + 1/(2sqrt2)]`
`= - [(sqrt3 + 1)/(2sqrt2)]`
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