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JAMB 1994 · UME · Q38

What is the value of sin⁡(−690∘)\sin(-690^\circ)?

Worked solution (try it first)
  1. Adding whole turns of 360∘360^\circ does not change the sine.
  2. Add two turns: −690∘+720∘=30∘-690^\circ + 720^\circ = 30^\circ.
  3. So sin⁡(−690∘)=sin⁡30∘=12\sin(-690^\circ) = \sin30^\circ = \frac12, option D.

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