A triangle has sides 15, 41, and 52. What is its area?
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I did it with the cosine and sine rule, but the answer is the same anyways
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haha me too :) But Heron's formula is faster :)
pythagorean theorem Try it. Do an altitude to the 52 side.
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I used the pythagorean theorem but it still didnot work.I am not sure can you show it to me.
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@Mardokay Mosazghi – The reason you guys couldn't use the pythagorean theorem was because this triangle is not a right triangle.
In this case, using Heron's Formula would be the easiest way to go (For me at least), and using cosine and sine laws is correct also.
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@Cameron Wong – That triangle was an obtuse triangle but splitting it into two right triangles was the method.
@Mardokay Mosazghi – this works only with right triangles use herons formula instead
Hahaha! That #Heron'sFormula was misleading. Just split the triangle into 9, 12, 15 and 9, 40, 41 triangles.
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Yep, that is one way to do it. However, it takes quite a bit of imagination to find that, so Heron's Formula would actually be much faster.
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No i think finding out the 2 triangles would be faster. Too much tedious calculation when one can see the 2 triangles. I thought there was probably a trick and found out the two triangles
but herons is still a viable option in solving this question
Much easier than my contorted solution.
Area=sqrt(s(s-a)(s-b)(s-c)) ; s=(a+b+c)/2 a=15,b=41,c=52 and s=54 ; Area=sqrt(54(54-15)(54-41)(54-52)) Area=sqrt(54(39)(13)(2)) Area=sqrt(54756) Area=234
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Or you can see this post of Daniel Liu: Beginner LaTeX Guide
The area formula for every triangle is known and is A = 2 h e i g h t ∗ b a s e . So, first of all there is necessary to calculate the height of the triangle, for that we write the next two equations system: ( 5 2 − x ) 2 + ( h ) 2 = ( 4 1 ) 2 ; ( x ) 2 + ( h ) 2 = ( 1 5 ) 2 . Now we procede to calculate the systems equations by the reduction method: ( 5 2 − x ) 2 + ( h ) 2 = ( 4 1 ) 2 . − ( x ) 2 − ( h ) 2 = − ( 1 5 ) 2 ( 5 2 − x ) 2 − ( x ) 2 = ( 4 1 ) 2 − ( 1 5 ) 2 ⇒ ( 5 2 ) 2 − 2 ∗ 5 2 ∗ x + ( x ) 2 − ( x ) 2 = 1 6 8 1 − 2 2 5 = 1 4 5 6 ⇒ − 2 ∗ 5 2 ∗ x = 1 4 5 6 − ( 5 2 ) 2 = − 1 2 4 8 ⇒ x = 1 2 4 8 / 2 ∗ 5 2 = 1 2 .
Now we substitute the x in one of the two equations to know the value of h. ( h ) 2 = ( 1 5 ) 2 − ( 1 2 ) 2 = 8 1 ⇒ h = 8 1 = 9
Hence the area of the triangle is A = 2 5 2 ∗ 9 = 2 3 4 . □
The area is S ∗ ( S − a ) ∗ ( S − b ) ∗ ( S − c ) S = 2 ( a + b + c ) and a=15 ,b=41 and c=52
a,b,c be the side length
p = ( a + b + c ) / 2 = ( 1 5 + 4 1 + 5 2 ) / 2 = 5 4
Area = p × ( p − a ) × ( p − b ) × ( p − c ) = 5 4 × ( 5 4 − 1 5 ) × ( 5 4 − 4 1 ) × ( 5 4 − 5 2 ) = 5 4 7 5 6 = 2 3 4 .
Given sides are 1 5 , 4 1 , 5 2 . Let us take these sides as a , b , c respectively and s be the semi-perimeter of the triangle, i.e, half the perimeter of the triangle.
We shall use here Heron's formula which states that, Area = s ( s − a ) ( s − b ) ( s − c ) for a triangle of sides a , b , c and semi-perimeter s .
Perimeter of this triangle = 1 5 + 4 1 + 5 2 = 1 0 8 . So, s = 2 1 0 8 = 5 4
Area = 5 4 ( 5 4 − 1 5 ) ( 5 4 − 4 1 ) ( 5 4 − 5 2 )
= 5 4 × 3 9 × 1 3 × 2
= 9 × 6 × 1 3 × 3 × 1 3 × 2 = 3 2 × 1 3 2 × 6 2 = 3 × 1 3 × 6 = 2 3 4
We can use another form of Heron's formula:
4 1 4 a 2 b 2 − ( a 2 + b 2 − c 2 ) 2
Which for our question can be written as:
4 1 4 ∗ 1 5 2 ∗ 4 1 2 − ( 1 5 2 + 4 1 2 − 5 1 2 ) 2
This can be simplified to:
4 1 1 5 1 2 9 0 0 − 6 3 6 8 0 4
Which can be further simplified to:
4 1 8 7 6 0 9 6
which then equals to
4 1 ∗ 9 3 6
So our answer is:
4 9 3 6 = 2 3 4
Answer:
= 2 3 4
compute any angle by cosine law
5 2 2 = 1 5 2 + 4 1 2 − 2 ( 1 5 ) ( 4 1 ) c o s B
B = 1 3 0 . 4 5 d e g r e e s
A = 2 1 ∗ 1 5 ∗ 4 1 ∗ s i n 1 3 0 . 4 5 = 2 3 4
First find for the semi-perimeter:
s = ( 15 + 41 + 52 ) / 2 = 54
then using Heron's Formula:
A = sq. root of (54 x (54-15) x (54 - 41) x (54 - 52)) A = 234 sq. units :)
area of a scalene triangle (whose all sides are different) is given by (s(s-a)(s-b)(s-c))^0.5 where s=(a+b+c)/2, a,b,c being sides of triangle.
You can USE the Heron's Formula in solving the area of a triangle (if the lengths of 3 sides are already given)
Let a, b, c be the lengths of the sides of a triangle.
Area = square root of p(p-a) (p-b) (p-c)
where "p" is half the perimeter, or:
a + b + c / 2 [[this can be understand as, "the SUM of 3 sides DIVIDED by 2"]]
This is how it goes:
a = 15
b = 41
c = 52
p = 54 [[ 15+41+52 = 108 DIVIDED BY 2]]
A = square root of 54 (54 - 15) (54 - 41) (54 - 52)
A = square root of 54 (39) (13) (2)
A = square root of 54756
Therefore, the area is 234.. :)
The semi-perimeter of the triangle is (15+41+52)/2 whose answer is 54.Now by heron's formulae we can derive the area easily. The heron's formulae is the square root of {s(s-a)(s-b)(s-c)} where s is the semi-perimeter and a , b and c are the sides of the triangle.
sol:- let a =15, b=41,c=52 S=a+b+c/2 =15+41+52/2=>54 A=(s(s-a)(s-b)(s-c))^1/2 here a is area of triangle =(54(54-15)(54-41)(54-52))^1/2 =234
We know if 15^2 = 12^2 + 9^2 and 41^2 = 40^2 + 9^2 ,also 40 + 12 = 52. Because it can make a triangle has side 15, 41, 52. So, the areas is (9 x 52 )/2 = 9 x 26 = 234. Answer : 234
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By Heron's Formula we have the area of triangle as s ( s − a ) ( s − b ) ( s − c ) where a , b , c are the side lengths and s is the semi-perimeter which is equal to 2 1 5 + 4 1 + 5 2 in this case. Plugging in the values gives us 5 4 ( 5 4 − 1 5 ) ( 5 4 − 4 1 ) ( 5 4 − 5 2 ) = 2 3 4