An equilateral triangle is circumscribed, find the area of the triangle
Give your answer to 3 decimal places.
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How did you get BC and AM?
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Ritu, sorry, I didn't explain it clearly. Sorry also B C = tan 3 0 ∘ 2 . Thanks for your questions, I have edited the solution.
We note that ∠ O B C = 3 0 ∘ . Let the radius of the incircle be r = 1 . Then B M r = tan 3 0 ∘ ⇒ B M = tan 3 0 ∘ r and B C = 2 B M = 2 × tan 3 0 ∘ r = 2 × 3 1 1 = 2 3 .
Again, ∠ O A B = 3 0 ∘ and A M = A O + O M , O M = r = 1 and A O r = sin 3 0 ∘ ⇒ A O = sin 3 0 ∘ r = sin 3 0 ∘ 1 . Therefore, A M = 1 + sin 3 0 ∘ 1 .
You can divide the triangle into 6 congruent 30-60-90 triangles. 1 being the side opposite to the 30 degree angle. Hence, the base of the smaller triangle will be sqrt(3). Using this, we can find the area of the smaller triangle, [1xsqrt(3)]/2=0.866~. We multiply the area by 6, since we divided the triangle into 6 congruent parts, getting the answer 6x0.866=5.196.
If we add the top of the triangle with the center of the circle we will get another triangle there.In this case we know that the hypotenuse is twice the radius . The radius of the circle is 1 so, the hypotenuse is 2 × 1 now use the theorem of the pithagoras x 2 + 1 2 = 2 2 ;[Base=x] so, x= 3 now, the length of equilateral triangle is 2 × x so, 2 × 3 =3.46) here a=3.46 ;[a is the length of the equilateral triangle] now, we know the formula of the area of equilateral triangle
by calculating we will get the area of the equilateral triangle so, the answer is 5.2
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Let the triangle be △ A B C , A being at the top, B C the base, and the center of the unit radius incircle be O . Then A O , B O and C O divide internally the ∠ A , ∠ B and ∠ C respectively. Let the incircle touches B C at M . Due to symmetry, M is the midpoint of B C .
The area of the triangle = 2 1 × B C × A M
= 2 1 ( 2 × B M ) ( A O + O M )
= 2 1 ( 2 × tan 3 0 ∘ 1 ) ( 1 + sin 3 0 ∘ 1 )
= 2 1 ( 3 1 2 ) ( 1 + 2 1 1 )
= 2 1 ( 2 3 ) ( 1 + 2 ) = 3 3 ≈ 5 . 1 9 6