Joshua T. answered 15d
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This is a great question about inverse trigonometric functions!
Finding the inverses of trigonometric functions is similar to using inverse operations in algebra because both processes “undo” a previous operation to find the original value. In algebra, inverse operations, such as addition and subtraction or multiplication and division, are used to isolate a variable and return to the starting number. For example, if y=3x+5, we would subtract 5 and then divide by 3 to solve for x, effectively reversing what was done to it.
In trigonometry, inverse functions like sin−1(), cos−1(), and tan−1() serve the same purpose by reversing the effect of the trigonometric functions to find the angle that produced a given ratio. It’s important to use the word “functions” instead of “ratios” because we are referring to the mathematical operations (sine, cosine, tangent) themselves, not just the numerical ratios they produce. The inverse trigonometric functions work backward from a known ratio to recover the original angle, just as inverse operations in algebra work backward to recover the original number.
Put simply, inverse trig functions undo the trig functions just like inverse operations undo algebraic steps.