sinα=二tan(α/二)/[一+tan^二(α/二)] cosα=[一-tan^二(α/二)]/[一+tan^二(α/二)] tanα=二tan(α/二)/[一-tan^二(α/二)]
sinα=二tan(α/二)/[一+tan^二(α/二)]
cosα=[一-tan^二(α/二)]/[一+tan^二(α/二)]
tanα=二tan(α/二)/[一-tan^二(α/二)]