Answer:
When we know all 3 sides, we use Heron's Formula
area = sqrt [s *(s-a) * (s-b) * (s-c)]
where "s" is the semi-perimeter which in this case equals
s = (6 + 8 + 12) / 2 = 13
area = sqrt [13 * 5 * 7 * 1]
area = sqrt 455
area = 21.3307290077
area = 21.33 square feet (rounded)
Step-by-step explanation:
Answer:
50
Step-by-step explanation:
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A stuntman jumping off a 20-m-high building is modeled by the equation h = 20 – 5t2, where t is the time in seconds. A high-speed camera is ready to film him between 15 m and 10 m above the ground. For which interval of time should the camera film him?
Answer:

Step-by-step explanation:
Given:
A stuntman jumping off a 20-m-high building is modeled by the equation
-----------(1)
A high-speed camera is ready to making film between 15 m and 10 m above the ground
when the stuntman is 15m above the ground.
height
Put height value in equation 1





We know that the time is always positive, therefore 
when the stuntman is 10m above the ground.
height
Put height value in equation 1







Therefore ,time interval of camera film him is 