抽象函数,其性质常常是隐而不露.但就其类型,最基本的有以下几种:(1)线性函数型抽象函数,如f(x+y)=f(x)+f(y);(2)指数函数型抽象函数,如f(x+y)=f(x)f(y);(3)对数函数抽象函数型,如f(xy)=f(x)+f(y)(4)三角函数型抽象函数,如f(x+y)f(x-y)=2f(x)f(y)(余弦函数型),f(x±y)=f(x)g(y)±f(y)g(x)(正弦函数型),f(x±y)=f(x)±f(y)/1-+f(x)f(y)(正切函数型).只要善于借用相应函数的相关性质,就 Abstract functions, whose nature is often hidden, but the most basic are the following types: (1) linear function abstract functions, such as f (x + y) = f (x) + f (y (2) Exponential function type abstract functions, such as f (x + y) = f (x) f (y); (3) Logarithmic function Abstract function type, such as f (xy) = f (x) + f (y) (4) trigonometric abstract functions such as f(x+y)f(xy)=2f(x)f(y) (cosine type), f(x±y)=f(x)g (y) ± f(y)g(x) (sine function type), f(x±y)=f(x)±f(y)/1-+f(x)f(y) (tangent function type ). As long as you are good at borrowing the relevant properties of the corresponding function,