Question 20 • AP Calculus AB - MA5186 A
Since cot x = −1.25, tan x = −1/1.25 = −0.8. A calculator gives the principal angle x = arctan(−0.8) ≈ −0.675 radians. Cotangent has period π, so all solutions are x = −0.675 + kπ, where k is any integer; this is choice B.
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