Question

I need help with those two questions

Answer 1

9) It helps to draw a picture.  Since one angle is 60°, the other angle is 120°.  When you draw the ddiagonal lines, you will see that you end up with a 30°-60°-90° triangle where √3 is the hypotenuse. The longest diagonal will be across from the 60° angle, which will be length a√3. The length of the hypotenuse is 2a. (Remember: a, a√3, 2a are lengths for this special triangle)
2a = √3 → a = √3/2. 
side across from 60° = a√3 = (√3/2)·√3 → side from across 60° = 3/2
Remember that this is only one-half of the diagonal of the rhombus so multiply that by 2.
Length of longest diagonal is 3.

10) Volume of a square pyramid = (1/3) B · h, where B is the area of the base
200 = (1/3)B(12)
 50  = B
Since the base is a square, then each side is √50 (which equals 5√2).

Now, to find the lateral edge, use Pythagorean Theorem (a² + b² = c²).
Height (a) = 12,  base (b) = 5√2, and lateral edge (c) is unknown.

(12)² + (5√2)² = c²
144  +   50     = c²
     194           = c²
     √194         = c

Lateral edge is √194.