Answer:
see explanation
Step-by-step explanation:
The sum to n terms of an arithmetic sequence is
=
[ 2a₁ + (n - 1)d ]
where a₁ is the initial value and d the common difference
Given
=
[ 10 + (n - 1)3 ]
Then by comparison
2a₁ = 10 ( divide both sides by 2 )
a₁ = 4 ← initial value
and d = 3 ← common difference
Thus
=
[ 10 + (7 × 3) ]
= 4(10 + 21)
= 4 × 31
= 124
Answer:
Step-by-step explanation:
They want you to see how radius is important. Just remember that one radian is one radius, that should help you see why radius is important.
They ask for the unit circle , that is a circle of one unit for the radius, which makes it super easy to calculate things for it, they ask what is the area, which is that famous formula, π , then they ask what's its circumference. which is that other famous formula 2πr
so to go all the way around a circle of one unit radius, it's 2π exactly or about 6.28..... units, call it meters, or feet or inches, it doesn't mater here.
the size of the circle doesn't matter here either, b/c we are using the radius , that relaationship doesn't change , all circles, what ever size , have this same relationship between the radius and radians. :P this is handy.
