Derive the correct equation for the critical angle (ϴ1) using Snell’s Law and ϴ2 = 90°. Be sure to show all the steps

please solve with all steps

Calculate the vertical deflection of point B and the horizontal movement at D shown in the figure. Consider that all the elements of the truss are linearly elastic and have sectional areas of 1800mm2. Also consider an E of 200,000N/mm2. Add the calculation process of solving the problem step by step and complete the table accordingly.   L F FB   ∂FB / ∂PB FD ∂FD/∂PD AE     - 2√2/3 PB  -2/3 √2     EB             EF             AB             BC             CD             BF             FD             FC

1.2 For the same beam as in problem 1.1, (a) Find the largest value of x-displacement. (b) Find the largest value of y-displacement. (c) Find the largest value of x-rotation. (d) Find the largest value of z-rotation. (Use the formulas in Roark's book for parts b and d.) Answers (a) 0.00955 in [to the right] (b) 5.915 in [up] (c) 0.124 rad (d) 0.1741 rad 20,000 in lb 1,000 lb 15,000 in lb 6,000 lb 100 lb/in 25' *5"* 10" 10" Cross-Section: Solid Circular with 2" Diameter Material Properties (Aluminum): E=10x10 psi E v=0.3 G= 2(1+v)