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Curated by: DFulks Math (15 videos)
What is cos(i)? Is "i" supposed to be an angle here? In this video, we show how the cosine function cos(z) is defined for complex numbers, and use it to find cos(i). Along the way we examine Euler's Formula, and we discover the close connection between the "hyperbolic" cosine function and the ordinary cosine function, which only becomes apparent in the realm of complex (imaginary) numbers. #complexnumbers #imaginarynumbers