Answer:
(d). 
Step-by-step explanation:
sin² β + cos² β = 1
cos (α + β) = cos α cos β - sin α sin β
cos α = √(1 - 
) = 21 / 29
cos β = 12 / 13
sin β = √(1 - 
) = 5 / 13
sin α = 20 / 29
cos (α + β) = 
× 
- 
× 
=
Given:
420 tropical fishes
angel fish = x
parrot fish = 6x
x + y = 420
y = 6x Choice D.
x + y = 420
y = 6x
x + 6x = 420
7x = 420
x = 420 / 7
x = 60 number of angelfish
y = 6x
y = 6(60)
y = 360 number of parrot fish
I think i’m not sure but i think the answer is (5,4) x=5 and y=4
Just use algebra to rearrange the terms so for s=1/2at^2 and solving for a we get 2s=at^2 so 2s/t^2=a
solving s=1/2at^2 for t gives 2s=at^2 which leads to 2s/a=t^2 so t=sqrt(2s/a)
filling in the numbers for 3 since a = 2s/t^2 we get a= (2(20.5m))/5s^2 =1.64m/s^2 the correct units in the answer indicate a possible correct answer since the units of acceleration are m/s^2.
4. using the value for a from question 3 and using 42.5 meters for s and solving for t we get sqrt((2s)/a) = sqrt((2*42.5m)/1.64m/s^2)= approximately 7.2s you can see the m's cancel and you are left s^2 as the units and the sqrt(s^2) = s so again the correct units indicate that 7.2s is probably correct. (These answers ARE correct though). checking the units gives a kinda quick assurance you are on the right path.
