In the month of June, the temperature in Johannesburg, South Africa, varies over the day in a periodic way that can be modeled approximately by a trigonometric function. The lowest temperature is usually around 3^\circ C3 ∘ C3, degrees, C, and the highest temperature is around 18^\circ C18 ∘ C18, degrees, C. The temperature is typically halfway between the daily high and daily low at both 10\text{ a. M.}10 a. M.10, start text, space, a, point, m, point, end text and 10\text{ p. M.}10 p. M.10, start text, space, p, point, m, point, end text, and the highest temperatures are in the afternoon.