how do you find the period of this equation? h= 25 cos pi/65 (t-15), where t=time in seconds.

Question

I know that the period should be 2pi/k, but I'm getting the wrong answer with that. The answer should be 130 seconds.

Answer 1

If h = 25cos[π/65(t-15)], the period will be 2π/(π/65) = 2π(65/π). The π's cancel and 2(65) = 130.

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desmos.com/calculator/wtouq79mj1