Question

If sin(theta°) = 0.5, and we know that cos (theta°) < 0, then what is the smallest possible positive value of theta?

Answer 1

150°

Explanation:

It is given that CosФ < 0 i.e CosФ is negative.

Therefore, the minimum the value of Ф for which CosФ <0 will be in the second quadrant i.e 90° < Ф < 180°.

Now it is also given that, Sin Ф =0.5 {the value of SinФ is positive because Sin value is positive in second quadrant.}

⇒ Ф =180° - Sin⁻¹ (0.5) = 180°-30° =150° (Answer)