double angle formula

例句：

1. 1.The double angle formula is used to solve problems involving two angles.
   双角公式用于解决涉及两个角的问题。
2. 2. In trigonometry, the double angle formula is crucial for calculating the sum of angles.
   在三角学中，双角公式对于计算角度之和至关重要。
3. 3.The double angle formula can be used to find the sum of two right angles in a right-angled triangle.
   双角公式可以用来求直角三角形中两个直角的和。