The graphs of \(f(x)=x^2-6x+9\) and \(g(x)=-x+5\) intersect at two points, \(P_1\) and \(P_2\), as shown. Let \(P_1\) be the point with the smaller x-coordinate.
The angle of intersection of two graphs is the acute angle formed by their tangent lines at the intersection point.
a) Find the coordinates of \(P_1\) and \(P_2\).
b) Find the slopes of the tangent lines to the graphs of \(f\) and \(g\) at each intersection point.
c) Find the angles of intersection \(\alpha_1\) at \(P_1\) and \(\alpha_2\) at \(P_2\). Give each answer in degrees to the nearest hundredth.

Hints
- Set the two function expressions equal to find their intersection points.
- The derivative gives the tangent slope at an input.
- Relate the slope of a line to its angle of inclination.
- Use the acute-angle formula for two lines, and make sure the result is at most \(90^\circ\).
Solution
1. Set the functions equal: \(x^2-6x+9=-x+5\). Then \(x^2-5x+4=0\), so \((x-1)(x-4)=0\). Thus, \(x=1\) or \(x=4\).
2. Using \(g(x)=-x+5\), the intersection points are \(P_1(1,4)\) and \(P_2(4,1)\).
3. Differentiate: \(f'(x)=2x-6\) and \(g'(x)=-1\). At \(P_1\), the slopes are \(f'(1)=-4\) and \(g'(1)=-1\). At \(P_2\), the slopes are \(f'(4)=2\) and \(g'(4)=-1\).
4. For two lines with slopes \(m_1\) and \(m_2\), \(\tan(\alpha)=\left|\frac{m_1-m_2}{1+m_1m_2}\right|\). At \(P_1\), \(\tan(\alpha_1)=\left|\frac{-4-(-1)}{1+(-4)(-1)}\right|=0.6\), so \(\alpha_1\approx30.96^\circ\).
5. At \(P_2\), \(\tan(\alpha_2)=\left|\frac{2-(-1)}{1+2(-1)}\right|=3\), so \(\alpha_2\approx71.57^\circ\).
Answer
a) \(P_1(1,4)\) and \(P_2(4,1)\)
b) At \(P_1\), the slopes are \(-4\) for \(f\) and \(-1\) for \(g\). At \(P_2\), the slopes are \(2\) for \(f\) and \(-1\) for \(g\).
c) \(\alpha_1\approx30.96^\circ\) and \(\alpha_2\approx71.57^\circ\)