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Algebra Difficulty 3.6 AMC 10/12 Find the answer

Given that aba \neq b, and a2sinθ+acosθπ4=0a^{2}\sin θ+a\cos θ- \frac {π}{4}=0, b2sinθ+bcosθπ4=0b^{2}\sin θ+b\cos θ- \frac {π}{4}=0, the position relationship between the line connecting the two points ((a,a2)((a,a^{2}), (b,b2))(b,b^{2})) and the unit circle is (( ))

Pick one

Solution

Since a2sinθ+acosθπ4=0a^{2}\sin θ+a\cos θ- \frac {π}{4}=0, b2sinθ+bcosθπ4=0b^{2}\sin θ+b\cos θ- \frac {π}{4}=0, we have {cosθ=π(a+b)4ab sinθ=π4ab\begin{cases} \cos θ= \frac {π(a+b)}{4ab} \ \sin θ=- \frac {π}{4ab}\end{cases}

Given that sin2θ+cos2θ=1\sin ^{2}θ+\cos ^{2}θ=1, we get ab1+(a+b)2=π4\frac {ab}{ \sqrt {1+(a+b)^{2}}}= \frac {π}{4}

The equation of the line passing through the two points ((a,a2)((a,a^{2}), (b,b2))(b,b^{2})) is ((b+a)xyab=0)((b+a)x-y-ab=0)

The expression ab1+(a+b)2=π4\frac {ab}{ \sqrt {1+(a+b)^{2}}}= \frac {π}{4} indicates that the distance between (0,0)(0,0) and ((b+a)xyab=0)((b+a)x-y-ab=0) is π4\frac {π}{4}

Therefore, the line intersects with the circle x2+y2=1x^{2}+y^{2}=1.

Hence, the answer is C\boxed{\text{C}}.

Using the given equations, we find sinθ\sin θ and cosθ\cos θ; using the square relationship of trigonometric functions, we get the equation that aa and bb satisfy; using the two-point form, we find the equation of the line, and using the formula for the distance between a point and a line and the condition for a line to be tangent to a circle, we find the equation of the circle.

This problem tests the relationship between a line and a circle, mainly examining the square relationship of trigonometric functions, the two-point form to find the equation of a line, the formula for the distance between a point and a line, and the condition for a line to be tangent to a circle.

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.