Các công thức hạ bậc

  Các công thức hạ bậc:

• \(sin^2\alpha= \dfrac{1}{2}(1-cos2\alpha)\)
• \(cos^2\alpha= \dfrac{1}{2}(1+ cos2\alpha)\)
• \(tan^2\alpha= \dfrac{1-cos2\alpha}{1+cos2\alpha}\)
• \(sin^4\alpha= \dfrac{1}{8}(cos4\alpha-4cos2\alpha+\dfrac{6}{2})\)
• \(cos^4\alpha= \dfrac{1}{8}(cos4\alpha+4cos2\alpha+\dfrac{6}{2})\)
• \(sin^5\alpha= \dfrac{1}{16}(sin5\alpha-5sin3\alpha+10sin\alpha)\)
• \(cos^5\alpha=\dfrac{1}{16}(cos5\alpha+5cos3\alpha+10cos\alpha)\)