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7/10

A Parallel Line Turns Tangent

The parabola C:y2=2pxC:y^2=2px (p>0p>0) has focus FF, and its directrix meets the xx-axis at a point DD. A line through FF meets CC at two points AA and BB, with

Parametrizationconic sections
5/10

Two Right Triangles Sharing a Hypotenuse

figure

Two right triangles ABCABC and ADCADC share the common hypotenuse AC=10AC = 10 and lie on opposite sides of it, so that $\…

plane geometrytrigonometryTriangle Geometry
7/10

Three Solutions Exactly

Let f(x)=(eax1)lnxf(x) = \left(\mathrm{e}^{ax} - 1\right)\ln x, where a>0a > 0.

1. When a=1a = 1, find the area of the triangle formed by the two coordinate axes and the tangent line to the cur…

functionsExtremacalculusSubstitution+1
7/10

Symmetric Points on an Ellipse

Two distinct points AA and BB on the ellipse x22+y2=1\dfrac{x^2}2+y^2=1 are symmetric about the line y=mx+12y=mx+\dfrac 12.

1. Find the range of mm. 2. Find the maximum area of $\triangle…

Affine Transformationconic sectionsAM-GManalytic geometry+1
8/10

Counting Bisecting-Midpoint Values

In a cube ABCD-A1B1C1D1ABCD\text{-}A_1B_1C_1D_1, let PP be a moving point on the four sides of the square A1B1C1D1A_1B_1C_1D_1, OO the center of the square ABCDABCD, and M,NM,N the midpoints of $AB,…

Parametrizationsolid geometryvectors
5/10

A Right Angle in the Complex Plane

Let f(z)=z219zf(z) = z^2 - 19z. There is a complex number zz such that the points corresponding to zz, f(z)f(z), and f(f(z))f(f(z)) in the complex plane are the vertices of a right triangle who…

complex numbersplane geometryQuadratic Equations
8/10

A Cubic Functional Equation

Find all functions f:RRf:\mathbb R\to\mathbb R such that for all x,yRx,y\in\mathbb R,

f(x3)+f(y3)=(x+y)[f(x2)+f(y2)f(xy)].f(x^3)+f(y^3)=(x+y)\bigl[f(x^2)+f(y^2)-f(xy)\bigr].
functionsSubstitutionalgebraFunctional Equations
7/10

A Vertex from the Euler Line

A triangle ABCABC has vertices A(2,0)A(-2,0) and B(0,4)B(0,4), and its Euler line has equation l:x+y2=0l:x+y-2=0. (The Euler line joins the circumcenter OO and orthocenter HH, with $2\overright…

analytic geometryTriangle Geometryvectors
9/10

An Interior Point Minimum

Let M(x0,y0)M(x_0, y_0) be a point in the first quadrant interior to the hyperbola x2a2y2b2=1\dfrac{x^2}{a^2} - \dfrac{y^2}{b^2} = 1 (a,b>0a, b > 0). Lines through MM meet the right branch at AA

AM-GManalytic geometryinequalityVieta's Formulas+1
6/10

Shaded Area in a Regular Dodecagon

figure

A regular dodecagon has area 144144. Find the area of the shaded region shown in the figure.

plane geometryTrigonometric IdentitiesTriangle Geometry
5/10

The Bottom of a Recurrence

A sequence {an}\{a_n\} satisfies a1=pa_1 = p, a2=p+1a_2 = p + 1, and

an+22an+1+an=n20a_{n+2} - 2a_{n+1} + a_n = n - 20

for all positive integers nn, where pp is a fixed real number.

For which val…

sequences
8/10

A Bound on Extreme-Value Sums

Let f(x)=x22xlnx(a1)x+af(x) = \dfrac{x^2}{2} - x\ln x - (a-1)x + a.

1. If ff has two extreme points x1,x2x_1, x_2, find the range of aa. 2. Under that condition, if m>f(x1)+f(x2)m > f(x_1) + f(x_2) always hol…

ExtremacalculusMonotonicity

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