Let 'n' be the number of side of a regular polygon each angle are equal and sum of each angle equal to (n-2)×180. ∴For a regular pentagon have five equal side, n=5
∴ sum of each angle = (n-2)×180=3×180 = 540. and ecah angle = 540÷5=108°. Therefore ∠BCG = 108° and ∠ABC =108°
Here BE is one of the diagonal of regular pentagon ABCDE. BE divide ∠ABC in 1:2 ratio
Therefore ∠ABE : ∠CBE = 36: 72
∴ ∠GCB + ∠CBE = 108° +72°=180°
<u>the question is </u> Calculate the value of the copper in the coin
Step 1
Find the volume of the coin
we know that
the volume of a cylinder is equal to
where
r is the radius of the coin
h is the thickness of the coin
in this problem we have
Diameter=19 mm=1.9 cm
r=D/2------> r=1.9/2=0.95 cm
h=1.5 mm=0.15 cm
substitute the values in the formula
Step 2
<u>Find the mass of copper in the coin</u>
we know that
the density is equal to
Solve for the mass
we have
substitute in the formula
Step 3
<u>Find the cost</u>
we know that
the market price of the copper is $2.15 per pound
1 pound=453.592 grams
convert gram to pounds
3.785 gr=3.785/453.592=0.0083 pounds
0.0083*$2.15=$0.018=$0.02
therefore
<u>the answer is</u>
$0.02