This problem has been solved!• take the Pythagorean equation in this form, sin2 x = 1 – cos2 x and substitute into the First doubleangle identity cos 2x = cos2 x – sin2 x cos 2x = cos2 x – (1 – cos2 x) cos 2x = cos 2 x – 1 cos 2 x cos 2x = 2cos 2 x – 1 Third doubleangle identity for cosine Summary of DoubleAngles • Sine sin 2x = 2 sin xDouble Angle Formulas The trigonometric double angle formulas give a relationship between the basic trigonometric functions applied to twice an angle in terms of trigonometric functions of the angle itself Tips for remembering the following formulas We can substitute the values ( 2 x) (2x) (2x) into the sum formulas for sin \sin sin and
Trigonometric Identity With Pythagorens Sec 2x Sin 2x Cos 2x Tan 2x Youtube