Trigonometric Formulas

Sum / Difference of Angles Formulas.

1.       cos(A + B) = cos A cos B - sin A sin B

2.       cos(A - B) = cos A cos B + sin A sin B

3.       sin(A + B) = sin A cos B + cos A sin B

4.       sin(A - B) = sin A cos B - cos A sin B

5.       tan(A + B) = [ tan A + tan B ] / [ 1 - tan A tan B]

6.       tan(A - B) = [ tan A - tan B ] / [ 1 + tan A tan B]

Sum / Difference of Trigonometric Functions Formulas.

7.       sin A + sin B = 2 sin [ (A + B) / 2 ] cos [ (A - B) / 2 ]

8.       sin A - sin B = 2 cos [ (A + B) / 2 ] sin [ (A - B) / 2 ]

9.       cos A + cos B = 2 cos [ (A + B) / 2 ] cos [ (A - B) / 2 ]

10.       cos A - cos B = - 2 sin [ (A + B) / 2 ] sin [ (A - B) / 2 ]

Product of Trigonometric Functions Formulas.

11.       2 sin A cos B = sin (A + B) + sin (A - B)

12.       2 cos A sin B = sin (A + B) - sin (A - B)

13.       2 cos A cos B = cos (A + B) + cos (A - B)

14.       2 sin A sin B = - cos (A + B) + cos (A - B)

Multiple Angles Formulas.

15.       sin 2A = 2 sin A cos A

16.       cos 2A = cos ² A - sin ² A = 2 cos ² A - 1 = 1 - 2 sin ² A

17.       sin 3A = 3 sin A - 4 sin ³ A

18.       cos 3A = 4 cos ³ A - 3 cos A

Power Reducing Formulas.

19.       sin ² A = (1/2) [ 1 - cos 2A ]

20.       cos ² A = (1/2) [ 1 + cos 2A ] 

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