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secondary 3 | A Maths
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Pls help. Thank you
Date Posted: 5 months ago
Views: 111
interesting question. at first glance, does not seem possible to do without calculator, because 230° is not a special angle.
can solve by considering relationship between sine & cosine,
ie, sinθ = cos(90°-θ) is true for all θ.
RHS = sin(230) = cos(90-230) = cos(-140) = -cos(40).
-180°≤x≤180° implies -360°≤2x≤360°
(consider all other angles within given interval)
2x = -220, -140, 140, 220
x = -110, -70, 70, 110 (answer)
can solve by considering relationship between sine & cosine,
ie, sinθ = cos(90°-θ) is true for all θ.
RHS = sin(230) = cos(90-230) = cos(-140) = -cos(40).
-180°≤x≤180° implies -360°≤2x≤360°
(consider all other angles within given interval)
2x = -220, -140, 140, 220
x = -110, -70, 70, 110 (answer)
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