Answer:
•cos(s+t) = cos(s)cos(t) - sin(s)sin(t) = (-⅖).(-⅗) - (√21 /5).(⅘) = +6/25 - 4√21 /25 = (6-4√21)/25
•cos(s-t) = cos(s)cos(t) + sin(s)sin(t) = (-⅖).(-⅗) + (√21 /5).(⅘) = +6/25 + 4√21 /25 = (6+4√21)/25
cos(t) = ±√(1 - sin²(t)) → -√(1 - sin²(t)) = -√(1 - (⅘)²) = -⅗
sin(s) = ±√(1 - cos²(s)) → +√(1- cos²(s)) = +√(1 - (-⅖)²) = √21 /5
Step-by-step explanation:
gradient = slope or several other words.
it describes how strongly a line (or tangent to a bent curve) is going up or down or ... if it is changing at all.
it is represented by the ratio
(y coordinate change / x coordinate change)
when going from one point on the line to another.
in our case, when going from A to B we have
x changes by -2k (from 3k to k).
y changes by -11 (from 8 to -3).
so, the gradient or slope is
-11/-2k = 3
11/2k = 3
11 = 3×2k = 6k
k = 11/6
A = (33/6, 8) = (11/2, 8)
B = (11/6, -3)
