The first term of an arithmetic sequence is 7 and the sixth term is 22. find(a)the common difference; (2)(b)the twelfth term; (2)(c)the sum of the first 100 terms.

d = 3 , a₁₂ = 40 and S = 7775

In an arithmetic sequence the nth term and sum to n terms are

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,