Question #4cf0a

1 Answer
May 25, 2017

18sqrt(3)-2/3pi

Explanation:

First we need to solve for the intersections between the graphs.

17sintheta=9-sintheta
17sintheta+sintheta=9
18sintheta=9
sintheta=1/2
theta=sin^-1(1/2)
theta=pi/6

Now, the thing with trig functions is that they are periodic, so we need to find the next point that has sintheta=1/2 from theta=pi/6. In this case, sin((5pi)/6)=1/2.

So now we have the interval in which we have the area above y_1=9-sintheta and the area below y_2=17sintheta (Yellow area, Figure 1).

Desmos Figure 1

Now, we can integrate the two areas.

A_1=int_(pi/6)^(5/6pi)9-sintheta \quad d theta

A_2=int_(pi/6)^(5/6pi)17sintheta \quad d theta

A=A_2-A_1

Now, just a side note that the blue shaded area is just A_1+A_2

Let's integrate A_1 and ignore the constant

int \quad 9-sintheta \quad d theta=int \quad 9 \quad d theta - int \quad sintheta \quad d theta=x+costheta

So

int_(pi/6)^(5/6pi)9-sintheta \quad d theta=x+costheta \quad |_(pi/6)^(5/6pi)
=cos(5/6pi)-cos(pi/6)+5/6pi-pi/6
=-sqrt(3)-2/3pi

Let's integrate A_2 and ignore the constant

int\quad 17sintheta \quad d theta
=-17costheta

int_(pi/6)^(5/6pi)17sintheta \quad d theta=-17costheta \quad |_(pi/6)^(5/6pi)=17sqrt(3)

So, the area is 18sqrt(3)-2/3pi