20 March 2020 Sergiu Funieru The formula for cos (-a) [formula for the cosine of minus a] +1 The formula for sin (-a) [formula for the sine of minus a] Have you seen this? +1
![The formula for cos (-a) [formula for the cosine of minus a]](https://lunlun.com/wp-content/uploads/2020/03/The-formula-for-cos-a-formula-for-the-cosine-of-minus-a.png "The formula for cos (-a) [formula for the cosine of minus a]")