Find the sum of the first 20 terms of an arithmetic series if the first term is 10 and the twentieth term is 38.

[arithmetic sequences]

if correct

480

Step-by-step explanation:

To find the sum of the first n terms of an arithmetic series use the formula, n terms of an arithmetic sequence use the formula,

Sn=n(a1 + an)2

n=20

a1= 10

a20=38

20(10+38)/2

20(48)/2

960/2

480

So the ans is 480

the equation cos(35) =a/25 can be used to find the length of bc what is the length of bc? round to the nearest tenth

step-by-step explanation: