Final answer:
The true statement is that as the angle of an obtuse angle decreases, the sine decreases. Sine and cosine values change as the angle changes, with sine decreasing towards 90 degrees in the obtuse range and cosine increasing because it becomes less negative. The behavior of tangent is more complex due to its ratio nature.
Step-by-step explanation:
The correct statement is: As the measure of an obtuse angle decreases, the sine of the angle decreases. For an obtuse angle in the range of 90° to 180° degrees, as the angle decreases, the sine values will also decrease. This is due to the fact that sine is defined as the opposite over the hypotenuse in a right triangle, and as the angle approaches 90°, the length of the opposite side in relation to the hypotenuse decreases, leading to a smaller sine value. However, for cosine and tangent as the angle decreases from obtuse towards 90 degrees, the cosine values will increase since they are negative in this range (decreasing in negativity), and the tangent, being the ratio of sine over cosine, will also change accordingly, but its behavior will be more complex as it approaches negative infinity at 90 degrees then jumps to positive infinity just after 90 degrees in the obtuse range.