Question

Please help!!!! Will mark brainliest!! 18 points.

Answer 1

Method 1:

You can use the formula of an area of equilateral triangle:

$A=\dfrac{a^2\sqrt3}{4}$

a - length of side

We have a = 10 yd. Substitute:

$A=\dfrac{10^2\sqrt3}{4}=\dfrac{100\sqrt3}{4}=25\sqrt3\ yd^2\\\\\sqrt3\approx1.7\\\\A=25(1.7)=\boxed{42.5\ yd^2}$

Method 2:

Use the Pythagorean theorem (look at he picture).

$5^2+h^2=10^2$

$25+h^2=100$           subtract 25 from both sides

$h^2=75\to h=\sqrt{75}\\\\h=\sqrt{25\cdot3}\\\\h=\sqrt{25}\cdot\sqrt3\\\\h=5\sqrt3\ yd$

The formula of an area of a trinagle:

$A=\dfrac{1}{2}bh$

b - base

h - height

We have b = 10 yd and h = 5√3 yd. Substitute:

$A=\dfrac{1}{2}(10)(5\sqrt3)=(5)(5\sqrt3)=25\sqrt3\ yd\\\\\sqrt3\approx1.7\\\\A=25(1.7)=\boxed{42.5\ yd^2}$

Answer 2

Answer:

42.5

Step-by-step explanation:

A=sqrt(3)/4 a^2  where a is the side length

  = 1.7 /4 * 10^2

 =1.7/4 * 100

 = 1.7 * 25

=  42.5