例已知半径为R、r的两圆,它们的两条内公切线互相垂直。试求两外公切线与一条内公切线围成的三角形面积。本题除可应用海伦公式或用内切圆半径与三边长的积的一半关系求得三角形的面积外。还可用求三角形面积的基本公式来解,其解法如下: For example, two circles with radius R and r are known, and their two internal tangents are perpendicular to each other. Try to find the area of ​​the triangle enclosed by the tangents of the two males and one tangent. In addition to applying Helen’s formula or using half of the product of the radius of the inscribed circle and the length of the three sides, this problem can be obtained as the area of ​​the triangle. It can also be solved by the basic formula for the area of ​​the triangle. The solution is as follows: