Learn about the trigonometric angle addition identities, which help us discuss the trig values of sums of angles in terms of the trig values of the individual angles. For example, we can express sin(x+y) in terms of sin(x), sin(y), cos(x), and cos(y).
4438_Proof_of_the_sine_angle_addition_identity.html
4439_Proof_of_the_cosine_angle_addition_identity.html
4437_Using_the_cosine_double_angle_identity.html
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