Essential Trigonometry Without Geometry

value of sinx, enable the development of several important identities and analytic results in elementary ... = 2sinxcosx+ 2cosx( sinx) = 0 Since the derivative is 0, sin2 x+ cos2 xis a constant. Because sin0 = 0, and cos0 = 1, this constant must be 1. Next, we consider the identity for the sine of the sum of xand y. The proof in most elementary ... ................
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