Formula and method of explosive spike in college entrance examination mathematics 1
1, applicable condition: [straight line passing through the focus], which must have ecosA=(x- 1)/(x+ 1), where a is the included angle between the straight line and the focus axis, which is an acute angle.
X is the separation ratio and must be greater than 1. Note: The above formula is applicable to all conic curves. If the focus is internally divided (meaning that the focus is on the cutting line segment), use this formula; If it is divided (focusing on the extension line of the section), the right side is (x+ 1)/(x- 1), and the rest remains unchanged.
2. the periodicity of the function (note 3): 1, if f(x)=-f(x+k), then T = 2k.
3. If f(x)=m/(x+k)(m is not 0), then T = 2k3. If f(x)=f(x+k)+f(x-k), then T=6k. Note: a.
The period of a periodic function is infinite. B a periodic function may not have a minimum period, such as a constant function. C. periodic function plus periodic function is not necessarily a periodic function, for example, y=sinxy=sin pie x is not a periodic function.
4. The problem of symmetry (a problem that countless people can't understand) can be summarized as follows: 1, if it is satisfied on r (the same below): f(a+x)=f(b-x) is a constant, and the symmetry axis is x = (a+b)/2; 2. The images of functions y=f(a+x) and y=f(b-x) are symmetric about x=(b-a)/2; 3. If f(a+x)+f(a-x)=2b, the image of f(x) is symmetrical about the center of (a, b).