Find the second term of the arithmetic series described by a1=0.25, an=4, and sn=8.5 a2=

Step-by-step explanation:

an=4=a1+(n-1)*d=0.25+(n-1)*d

so (n-1)*d=4-0.25=3.75

Sn=a1*n+(n-1)*d

a1*n+3.75=8.5

0.25*n+3.75=8.5

-3.75                -3.75

0.25*n=8.5-3.75=4.75

n=4.75:0.25

n=19

so a19=a1+(19-1)*d=4

          0.25+18*d=4

           -0.25           -0.25

         18*d=3.75

           d=3.75/18

            d=0.208

so  a2=a1+0.208=0.25+0.208=0.458

a2=0.458

answer:  

step-by-step explanation:

here x represents the height of the pole,

and, the height of the shadow of the pole is 12 feet.

also, the angle of elevation from the top of the pole is 40°,

therefore,

by the low of sine,

which is the required equation for finding the value of x,