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AdorableApatosaurus7671

Good evening! I have a question about finding the rule of sine and cosine function. For other questions, I just simply draw a rectangle to identify where one period starts and ends, and it worked perfectly (I just need to calculate the distance between two points). For this question, it’s hard to find numbers. But I remember that the distance between max and min is a half period right? When I did in this way, it doesn’t work. I need a bit more clarification. Thank you so much! :)

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Andréa C

Hello, AdorableApatosaurus7671!

Congrats, you found the right value for parameter b based on the right explanation! 

You most likely got marked the answer as incorrect because you forgot the parenthesis around π/4(x). The values in the cosine must be precisely shown. Otherwise, it looks as if it’s only π/4.

https://www.alloprof.qc.ca/en/students/vl/mathematics/finding-the-rule-of-a-cosine-function-m1179

Do not hesitate to ask more questions!