Which equation correctly uses the law of cosines to solve for the length s?

Choice D

s^2 = 9^2 + 10^2 - 2(9)(10)cos(100)

Explanation:

Consider the pythaorean theorem

a^2 + b^2 = c^2

which is the same as saying

c^2 = a^2 + b^2

If we tack on "-2ab*cos(C)", then we end up with

c^2 = a^2 + b^2 - 2ab*cos(C)

which is one form of the law of cosines. The side c is opposite angle C, and the two are on opposite sides of the equation. The 'a's and 'b's are on the right side with the angle C.

Note if C = 90 degrees, then cos(C) = cos(90) = 0 which means the whole "-2ab*cos(C)" term goes to 0 and we'd be left with the pythagorean theorem again.

In this case, we replace c with s, replace 'a' with 9, replace b with 10, and C with 100.

Option (4)

Step-by-step explanation:

Cosine rule states,

(UT)² = (SU)² + (ST)² - 2(SU)(ST)cos(∠UST)

Here, UT is the opposite side of angle UST and two sides SU and ST are the adjacent sides.

∠UST is the included angle between SU and ST.

By this formula,

s² = 9² + 10² - 2(9)(10)cos(100°)

Therefore, Option (4) will be the answer.

5 pm

step-by-step explanation:

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for