sinα + cosα=√2 * [(1/√2)*sinα + (1/√2) * cosα]=√2 * [sinα*cos(π/4) + cosα*sin(π/4)] 注：sin(π/4) = cos(π/4) = 1/√2=√2 * sin(α + π/4) 注：二角和公式，sin(α + β) = sinα*cosβ + cosα*sinβ
