answer:Use the trig identity: #cos 2a = 2cos^2 a - 1# #cos 2(105) = cos 210 = cos (180 + 30) = -cos 30 = -sqrt3/2# Call c = cos 105. #-sqrt3/2 = 2c^2 - 1 --> 2c^2 = 1 - sqrt3/2# #c^2 = (1 - sqrt3/2)/2# #c = cos 105 = +- sqrt[(1 - sqrt3/2)/2]# Since arc 105 is on Quadrant II, its cos must be negative. Therefore: #c = cos 105 = - sqrt[(1 - sqrt3/2)/2]#

answer:The sum x+y can be found by simply adding the corresponding parts of x and y. Since both x and y contain the base e, we keep e the same and add the parts in front of it. For the real parts, we have 1+2=3, and for the imaginary parts, we have 3i+0i=3i. Thus, the sum is (3+3i)e.

answer:True. Revenue drivers refer to the methods by which a business generates income, such as through the sale of products or services. These revenue-generating activities are typically detailed in the "Economics of the Business" section, where the company's financial strategy is outlined.

answer:The balanced chemical equation for the reaction is: [2HI + Zn rightarrow H_2 + ZnI_2] From the stoichiometry, we see that 1 mole of hydrogen gas (H_2) is produced for every 2 moles of hydroiodic acid (HI). First, we calculate the number of moles of HI: [n_{HI} = cV = (0.185 text{ mol/L}) times (150 text{ mL}) times left(frac{1 text{ L}}{1000 text{ mL}}right) = 0.02775 text{ mol}] Hence, the number of moles of H_2 produced is: [n_{H_2} = frac{n_{HI}}{2} = frac{0.02775 text{ mol}}{2} = 0.013875 text{ mol}] At STP, 1 mole of any gas occupies 22.4 L. So, the volume of H_2 is: [V_{H_2} = n_{H_2} times V_{molar} = (0.013875 text{ mol}) times (22.4 text{ L/mol}) = 0.311 text{ L}] Therefore, the volume of hydrogen gas formed at STP is 0.311 L.