Home » Further Mathematics » Evaluate (cos (frac{pi}{2} + frac{pi}{3}))

Evaluate (cos (frac{pi}{2} + frac{pi}{3}))

Evaluate (cos (frac{pi}{2} + frac{pi}{3}))

  • A.
    (frac{-2}{sqrt{3}})
  • B.
    (frac{-sqrt{3}}{2})
  • C.
    (frac{sqrt{3}}{4})
  • D.
    (frac{4}{sqrt{3}})
Correct Answer: Option B
Explanation

(cos (x + y) = cos x cos y – sin x sin y)

(cos (frac{pi}{2} + frac{pi}{3}) = cos frac{pi}{2} cos frac{pi}{3} – sin frac{pi}{2} sin frac{pi}{3})

= ((0 times frac{1}{2}) – (1 times frac{sqrt{3}}{2}))

= (0 – frac{sqrt{3}}{2} = -frac{sqrt{3}}{2})