Since they are similar, the dimensions are in the same ratio. L1 = 5, L2 = 15, so they are in a 3:1 ratio. So if V1 = 60, then W1×H1 = 60/5 = 12
W2 must also be 3×W1 and H2 3×H1, and
3×3 = 9. So take 12×9 (W×H1×9) ×15 (L2) = V2
V2 = 12×9×15 = 1620 cm^3
Let me know the right answer when you find out!
False........................
If m ACD = 30 => m DCB = 60.
In triangle ACD:



AC^{2}+CB^{2}=AB^{2} => AB=

=32.
=> P=16+32+

=48 +

.
Step 1: Convert
, which is in radians into degrees. To convert it multiply by 

900/12
75
Step 2: 75 degrees isn't on the unit circle but 45 degrees and 30 degrees is. Since 45 + 30 = 75 you can use the cosine of 45 and 30 to find the exact value
cos45 = 
cos30 =
Step 3: Add the cos45 and cos30 to get cos5pi/12

Hope this helped!