Question 13 • Mathematics III
Subtract 4π from 19π/4 to get 3π/4, so the angles are coterminal. The angle 3π/4 lies in Quadrant II and has reference angle π/4, where sine is √2/2. Thus cosecant(3π/4) = 1/(√2/2) = √2, so Haruto is correct, as choice A states.
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