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JAMB 2015 · UTME · Q27

Which of the following is a sketch of y=3sin⁡xy = 3\sin x?

−π−π/2π/2π3−3A.−π−π/2π/2π3−3B.−π−π/2π/2π3−3C.−π−π/2π/2π3−3D.
Worked solution (try it first)
  1. At x=0x = 0, y=3sin⁡0=0y = 3\sin 0 = 0.
  2. At x=π2x = \frac{\pi}{2}, y=3y = 3.
  3. At x=−π2x = -\frac{\pi}{2}, y=−3y = -3.
  4. Sketches C and D do not pass through the origin, so they are out.
  5. Sketch B passes through the origin, rises to 3 at π2\frac{\pi}{2} and falls to −3-3 at −π2-\frac{\pi}{2}, so the answer is option B.

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