public void Cosine_Test()
{
var calculator = new Calculator1();
Assert.AreEqual(0, calculator.Cosine((Math.PI) / 2.0));
Assert.AreEqual(0, calculator.Cosine((3.0 * Math.PI) / 2.0));
Assert.AreEqual(1, calculator.Cosine(0));
Assert.AreEqual(0.5, calculator.Cosine(Math.PI / 3.0));
Assert.AreEqual(-1, calculator.Cosine(Math.PI));
}