Suppose that, during an experiment, the temperature of a substance in degrees Celsius at time t may be modeled by the equation . Find all values of t for which the temperature of the substance is equal to Celsius. [Hint: Start by drawing a sketch of C(t).]

Solutions with base angle in quadrant III: +

Solutions with base angle in quadrant IV: +

Solutions with base angle on an axis: +


where is any integer, and all base angles are between and .

Use radian measure and enter your answers using at least four significant digits.