What "CO" in COsine Means

Take a few minutes to interact with the applet below. Then, answer the questions that follow.
In the right triangle above, what is the relationship between the blue angle and pink angle? (What vocabulary term/adjective describes the relationship between these 2 angles?)
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Fill in the blank with the correct word: The _____________ of the blue angle is the percentage displayed.
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Fill in the blank with the correct word: The ___________________ of the pink angle is the percentage displayed.
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Thus, we can conclude that if 2 angles are ______________________ (see your answer to (1)), then the __________ of one angle is equal to the ____________________ of its ___________________ ! Notice how the first 2 letters of the last 2 blanks are the same? Why is this?
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Information: What "CO" in COsine Means