Which function will have a y -intercept at negative 1 and an amplitude of 2 ?

The amplitude of a sine or cosine function is the absolute value of the coefficient in front of it. Choices A and C have amplitude 2. At x = 0, sin(0) = 0, so choice A gives a y-intercept of −2(0) − 1 = −1. Choice C instead gives −2(1) − 1 = −3 because cos(0) = 1.

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