If p=q and q=p exist at the same time, then p is both a sufficient condition and a necessary condition for q, which is a necessary and sufficient condition for q for short.

Master the signs of trigonometric function values of angles in each quadrant and trigonometric function values of special angles such as 0, 30, 45, 60, 90,180, 270 and 360.

Exponential function: This function applied to the value x is written as exp(x). It can also be written as ex, where e is a mathematical constant and the base of natural logarithm, which is about equal to 2.7 1828 1828, also called Euler number.

Domain: x∈R, which refers to all real numbers (-∞,+∞), that is, r; Range: for all exponential functions, y = a x. His a satisfies a>0 and a≠ 1, which means y >；; 0。 So the range is (0, +∞). You can also use A= 1, in which case the range is always 1.

In general, the function y = logax(a >；; 0, and a≠ 1) is called logarithmic function, that is, a function with power (real number) as independent variable, exponent as dependent variable and base constant as constant is called logarithmic function. Where x is the independent variable and the domain of the function is (0, +∞). It is actually the inverse function of exponential function, which can be expressed as x=ay. Therefore, the stipulation of a in exponential function is also applicable to logarithmic function.