Tetrahedral pyramid

Calculate the regular tetrahedral pyramid's volume and surface if the area of the base is 20 cm2 and the deviation angle of the side edges from the plane of the base is 60 degrees.

Correct answer:

V =  36.51 cm3
S =  72.915 cm2

Step-by-step explanation:

S1=20 cm2 Φ=60   S1 = a2 a=S1=20=2 5 cm4.4721 cm  u=2 a=2 4.4721=2 10 cm6.3246 cm  h=2u tanΦ=2u tan60° =26.3246 tan60° =26.3246 1.732051=5.47723 cm  V=31 S1 h=31 20 5.4772=36.51 cm3
b=h2+(a/2)2=5.47722+(4.4721/2)2=35 cm5.9161 cm  S2=a b/2=4.4721 5.9161/2=5 7 cm213.2288 cm2  S=4 S2+S1=4 13.2288+20=72.915 cm2

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