When circle [tex]\( P \)[/tex] is plotted on a coordinate plane, the equation of the diameter that passes through point [tex]\( Q \)[/tex] on the circle is [tex]\( y = 4x + 2 \)[/tex]. Which statement describes the equation of a line that is tangent to circle [tex]\( P \)[/tex] at point [tex]\( Q \)[/tex]?

A. The slope of the tangent line is 4.
B. The slope of the tangent line is -4.
C. The slope of the tangent line is [tex]\(\frac{1}{4}\)[/tex].
D. The slope of the tangent line is [tex]\(-\frac{1}{4}\)[/tex].



Answer :

To determine the slope of the tangent line to circle [tex]\(P\)[/tex] at point [tex]\(Q\)[/tex], start with the information that the equation of the diameter passing through point [tex]\(Q\)[/tex] is [tex]\(y = 4x + 2\)[/tex].

1. Identify the Slope of the Diameter:
- The equation [tex]\(y = 4x + 2\)[/tex] is in slope-intercept form ([tex]\(y = mx + b\)[/tex]), where [tex]\(m\)[/tex] is the slope.
- The slope of the diameter is thus [tex]\(4\)[/tex].

2. Tangent Line Relationship:
- A tangent line at any point on a circle is perpendicular to the radius (or diameter) at that point.
- If two lines are perpendicular, the product of their slopes is [tex]\(-1\)[/tex].

3. Find the Slope of the Tangent Line:
- Let [tex]\(m_{\text{diameter}}\)[/tex] be the slope of the diameter, which is [tex]\(4\)[/tex].
- The slope [tex]\(m_{\text{tangent}}\)[/tex] of the tangent line will be the negative reciprocal of [tex]\(m_{\text{diameter}}\)[/tex].
- [tex]\(m_{\text{tangent}} = -\frac{1}{m_{\text{diameter}}}\)[/tex].
- Therefore, [tex]\(m_{\text{tangent}} = -\frac{1}{4}\)[/tex].

4. Conclusion:
- The slope of the tangent line is [tex]\(-\frac{1}{4}\)[/tex].

Thus, the correct answer is:
D. The slope of the tangent line is [tex]\(-\frac{1}{4}\)[/tex].