A wire of length 5 0 c m is to be bent in the form of a parallelogram of area 5 0 c m 2 . If the angle between the adjacent sides is 3 0 0 , then the dimensions of the parallelogram are :
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3 0 o = 6 π @Maggie Miller ??? If yes, how?
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I was just using radians because they're more convenient. 3 0 ∘ = 6 π radians; just unit conversion.
Radians are the standard unit for angles; that's what calculators use.
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Any other way to do this without using radians @Maggie Miller ??
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@Sahba Hasan – I mean I could have written 3 0 ∘ instead of 6 π , radians don't change anything. I just didn't know how to type the degree symbol in my paint program.
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@Maggie Miller – ohh.. i understood it. Thanks...
The angle between adjacent sides is not just 3 0 ∘ , it is also 1 5 0 ∘ depending on which sides. Maybe it should say "the angle between two pairs of adjacent sides."
Let a represent the length of one side and let b represent the length of the other side of the parallelogram. You then have a pair of sides of length a and a pair of sides of length b as shown below.
Since you are given the perimeter of 50 you have 2(a+b) = 50.
You are given that one angle is 30 degrees (angle NMQ below) and can determine angle MNP is 150 degrees because MNP and NMQ are supplementary.
Drop a perpendicular from point M to point R and extend segment PN to point R (shown below). Angle MNR is supplementary to angle MNP so angle MNR = 30. This creates 30-60-90 triangle MNR. Through properties of 30-60-90 MR is
2
1
b.
MR is also the height of the parallelogram which gives the equation 2 1 ba = 50. (Area of 50 was given) .
Solving for a you get a = b 1 0 0
Substituting for a in 2(a+b)=50 gets you 2( b 1 0 0 +b)=50
2( b 1 0 0 +b)=50
b 1 0 0 + b = 25
100 + b^2 = 25b
b^2 - 25b + 100 = 0
(b - 5)(b-20) = 0
So b is either 5cm or 20cm making a either 20cm or 5cm respectfully. Either way the dimensions are 5cm and 20 cm.
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Let x be one side length of the parallelogram in cm. Since the perimeter of the paralellogram is 5 0 cm, the other side length is 2 5 − x cm.
Let h be the height of the paralellogram with respect to the base of length x . Since the area of the parellogram is 5 0 cm 2 , h = x 5 0 cm.
We have ( 2 5 − x ) ⋅ sin ( 6 π ) = x 5 0 . Multiplying by 2 x on both sides, we find 2 5 x − x 2 = 1 0 0 , so ( x − 5 ) ( x − 2 0 ) = 0 . Then x = 5 or x = 2 0 . In either case, the dimensions of the parallelogram are 5 cm and 2 0 cm.