Cos(A-B) = cosAcosB + sinAsinB
<span>
cos(</span>π/2 - θ) = cos(π/2)cosθ + sin(π/2)sinθ
π/2 = 90°
cos(π/2) = cos90° = 0. sin(π/2) = sin90° = 1
cos(π/2 - θ) = cos(π/2)cosθ + sin(π/2)sin<span>θ
</span>
= 0*cosθ + 1*sin<span>θ = </span>sin<span>θ
Therefore </span>cos(π/2 - θ) = sin<span>θ
QED </span>
Yes they are correct.
At least I'm pretty sure they are:)
If Dylan owes half as much as he used to that would imply that the 28$ would be divided by two which would be 14$, which means that half of what he owed 28$ would now be 14$.
The way to get the equation for the radius (r) is to get r by itself. So divide each side by 4pi
500/4pi=r^2
Now take the square root of each side to get the equation of r.
sqrt(500/4pi)=r
