The document contains 4 multiple choice questions with solutions:
1. The equation e
sin x
– e
–sin x
– 4 = 0 has exactly one real root.
2. If the vectors ˆˆa and b are two unit vectors, and the vectors ˆ ˆˆ ˆc a 2b and d 5a 4b= + = − are perpendicular to each other, then the angle between ˆˆa and b is 3π.
3. If a spherical balloon is filled with 4500π cubic meters of helium gas and leaks at a rate of 72π cubic meters per minute, then the rate the radius decreases 49 minutes later is 9/9