同角三角函数的基本关系式是三角函数中第一组恒等变换公式,主要涉及平方、倒数、商数三个关系,而诱导公式是在同角三角函数的基本关系式上推导出来的,它们在解答三角函数问题中都占有 The basic relational expression of the isogonal trigonometric function is the first set of identity transformation formulae in the trigonometric function. It mainly involves three relations of square, inverse, and quotient, and the induction formula is derived from the basic relational expression of the same-angle trigonometric function. They all occupy the solution to trigonometric problems.