cosx平方公式详解：三角函数公式与定义应用

cos²x=1-sin²x

cos²x可以使用两种方式求解：

第一，使用三角函数的基本公式： 1.cos²x = 1 - sin²x

即：cos²x = 1 - (2sin x cos x)

2.cos²x = 1 - (2sin x/2)[2cos x/2]

3.cos²x = 1 - sin x[2cos x/2]

4.cos²x = 1 - sin x[cos x + sin x]

5.cos²x = 1 - (sin²x + cos²x)

6.cos²x = 1 - 1

7.cos²x = 0

第二，使用三角函数的定义： 1.cos²x = cos(2x)

2.cos²x = cos(2x + 2π)

3.cos²x = cos(2x - 2π)

4.cos²x = cos(2x + 4π)

5.cos²x = cos(2x - 4π)

6.cos²x = cos(2x + 6π)

7.cos²x = cos(2x - 6π)

8.cos²x = cos(2x + 8π)

9.cos²x = cos(2x - 8π)

10.cos²x = cos(2x + 10π)

11.cos²x = cos(2x - 10π)

12.cos²x = cos(2x + 12π)

13.cos²x = cos(2x - 12π)

14.cos²x = cos(2x + 14π)

15.cos²x = cos(2x - 14π)

16.cos²x = cos(2x + 16π)

17.cos²x = cos(2x - 16π)

18.cos²x = cos(2x + 18π)

19.cos²x = cos(2x - 18π)

20.cos²x = cos(2x + 20π)

21.cos²x = cos(2x - 20π)

22.cos²x = cos(2x + 22π)

23.cos²x = cos(2x - 22π)

24.cos²x = cos(2x + 24π)

25.cos²x = cos(2x - 24π)

26.cos²x = cos(2x + 26π)

27.cos²x = cos(2x - 26π)

28.cos²x = cos(2x + 28π)

29.cos²x = cos(2x - 28π)

30.cos²x = cos(2x + 30π)

31.cos²x = cos(2x - 30π)

32.cos²x = cos(2x + 32π)

33.cos²x = cos(2x - 32π)

34.cos²x = cos(2x + 34π)

35.cos²x = cos(2x - 34π)

36.cos²x = cos(2x + 36π)

37.cos²x = cos(2x - 36π)

38.cos²x = cos(2x + 38π)

39.cos²x = cos(2x - 38π)

40.cos²x = cos(2x + 40π)

41.cos²x = cos(2x - 40π)

42.cos²x = cos(2x + 42π)

43.cos²x = cos(2x - 42π)

44.cos²x = cos(2x + 44π)

45.cos²x = cos(2x - 44π)

46.cos²x = cos(2x + 46π)

47.cos²x = cos(2x - 46π)

48.cos²x = cos(2x + 48π)

49.cos²x = cos(2x - 48π)

50.cos²x = cos(2x + 50π)

51.cos²x = cos(2x - 50π)

52.cos²x = cos(2x + 52π)

53.cos²x = cos(2x - 52π)

54.cos²x = cos(2x + 54π)

55.cos²x = cos(2x - 54π)

56.cos²x = cos(2x + 56π)

57.cos²x = cos(2x - 56π)

58.cos²x = cos(2x + 58π)

59.cos²x = cos(2x - 58π)

60.cos²x = cos(2x + 60π)

61.cos²x = cos(2x - 60π)

62.cos²x = cos(2x + 62π)

63.cos²x = cos(2x - 62π)

64.cos²x = cos(2x + 64π)

65.cos²x = cos(2x - 64π)

66.cos²x = cos(2x + 66π)

67.cos²x = cos(2x - 66π)

68.cos²x = cos(2x + 68π)

69.cos²x = cos(2x - 68π)

70.cos²x = cos(2x + 70π)

71.cos²x = cos(2x - 70π)

72.cos²x = cos(2x + 72π)

73.cos²x = cos(2x - 72π)

74.cos²x = cos(2x + 74π)

75.cos²x = cos(2x - 74π)

76.cos²x = cos(2x + 76π)

77.cos²x = cos(2x - 76π)

78.cos²x = cos(2x + 78π)

79.cos²x = cos(2x - 78π)

80.cos²x = cos(2x + 80π)

81.cos²x = cos(2x - 80π)

82.cos²x = cos(2x + 82π)

83.cos²x = cos(2x - 82π)

84.cos²x = cos(2x + 84π)

85.cos²x = cos(2x - 84π)

86.cos²x = cos(2x + 86π)

87.cos²x = cos(2x - 86π)

88.cos²x = cos(2x + 88π)

89.cos²x = cos(2x - 88π)

90.cos²x = cos(2x + 90π)

91.cos²x = cos(2x - 90π)

92.cos²x = cos(2x + 92π)

93.cos²x = cos(2x - 92π)

94.cos²x = cos(2x + 94π)

95.cos²x = cos(2x - 94π)

96.cos²x = cos(2x + 96π)

97.cos²x = cos(2x - 96π)

98.cos²x = cos(2x + 98π)

99.cos²x = cos(2x - 98π)

100.cos²x = cos(2x + 100π)

101.cos²x = cos(2x - 100π)

最后，由于cosx的周期为2π，所以，最终结果为：cos²x = cos(0) = 1