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The sides of a rhombu is 100 cm long and the length of the longer diagonal is 160 cm.
 a. Find the smaller angle between the sides ofthe rhombus.
 b. Find the length of the smaller diagonal.
 c. Find the area of the rhombus.

 Jan 4, 2015

Best Answer 

 #1
avatar+128407 
+5

a. We can use the Law of Cosines to find the larger angle "Θ" between the sides...we have

160^2  = 100^2 + 100^2 - 2(100)(100)cosΘ  simplify

cosΘ = 5600/(-2*100^2) = -7/25  ... find Θ by using the cosine inverse..

cos-1(-7/25)  = about 106.26°

And since adjacent angles in a rhombus are supplementary, the smaller angle between the sides = (180-106.26)= 73.74°

b. We can again use the Law of Cosines to find the length of the smaller diagonal.....call it "D"....so we have

D^2  = 100^2 + 100^2 - 2(100)(100)cos(73.74) = 14400.06859844   .. take the square root of this

D = about 120

 

c. The area is given by (1/2) the product of the diagonals  = (1/2)(160)(120) = 9600 sq units

 

 Jan 4, 2015
 #1
avatar+128407 
+5
Best Answer

a. We can use the Law of Cosines to find the larger angle "Θ" between the sides...we have

160^2  = 100^2 + 100^2 - 2(100)(100)cosΘ  simplify

cosΘ = 5600/(-2*100^2) = -7/25  ... find Θ by using the cosine inverse..

cos-1(-7/25)  = about 106.26°

And since adjacent angles in a rhombus are supplementary, the smaller angle between the sides = (180-106.26)= 73.74°

b. We can again use the Law of Cosines to find the length of the smaller diagonal.....call it "D"....so we have

D^2  = 100^2 + 100^2 - 2(100)(100)cos(73.74) = 14400.06859844   .. take the square root of this

D = about 120

 

c. The area is given by (1/2) the product of the diagonals  = (1/2)(160)(120) = 9600 sq units

 

CPhill Jan 4, 2015
 #2
avatar+90 
0

Thank you very much :)

 Jan 4, 2015

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