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7/10

Birthday Multiples

Joey, Chloe, and their daughter Zoe share a birthday. Joey is one year older than Chloe, and Zoe turns exactly 11 today. Today Chloe's age is an integer multiple of Zoe's age, and…

Diophantine Equationsnumber theoryCounting
7/10

An Acute Triangle Bound

In an acute triangle ABCABC, the sides opposite A,B,CA, B, C are a,b,ca, b, c. Given

sin(AB)cosB=sin(AC)cosC,asinC=1,\frac{\sin(A - B)}{\cos B} = \frac{\sin(A - C)}{\cos C}, \qquad a\sin C = 1,

find the maximum va…

Law of SinestrigonometryExtremaTrigonometric Identities+1
6/10

Modulus Extremes of a Cubic

Let zz be a complex number with z=1|z| = 1. Find the maximum and minimum values of

z3z+2.\left|z^3 - z + 2\right|.
complex numbersExtremacalculusTrigonometric Identities
7/10

Zeros of a Cosine Hybrid

The function ff is of the form f(x)=kxf(x) = \dfrac{k}{x}, and the curve g(x)=f(x)cosx+bg(x) = f(x)\cos x + b has tangent line y=6πx+2y = -\dfrac{6}{\pi}x + 2 at x=π2x = \dfrac{\pi}{2}.

1. Find g(x)g(x). 2…

functionsExtremacalculusMonotonicity
5/10

A Triangle from Three Clues

In triangle ABCABC, the sides opposite angles A,B,CA, B, C are a,b,ca, b, c respectively. Given that

2sinC=csinB,acosBc=1,2\sin C = c\sin B, \qquad a\cos B - c = 1,

and the area of triangle ABCABC is $\d…

plane geometryLaw of SinestrigonometryLaw of Cosines
7/10

A Parabola Meets an Exponential

Let f(x)=m(x2m)(x+m+1)f(x) = m(x - 2m)(x + m + 1) and g(x)=ex1g(x) = e^x - 1. Determine, with proof, which of the following are true:

1. when m=1m = 1, the equation f(x)=g(x)f(x) = g(x) has exactly one real so…

functionscalculusMonotonicityCasework
9/10

Rainbow-Free Colorings

Color 1,2,,n1, 2, \dots, n with kk colors so that no three distinctly colored numbers form an arithmetic progression. Let f(n)f(n) be the largest such kk. Prove that

log3n\l\log_3 n \l…
combinatoricsArithmetic Progressionnumber theoryInduction+1
9/10

Triangle-Preserving Curve Families

A family of curves Γm\Gamma_m is called triangle-preserving if for every triangle ABCABC, some curve in the family contains three points P,Q,RP,Q,R with PQR\triangle PQR congruent to …

plane geometrySimilar TrianglesCirclesanalytic geometry+1
6/10

Maximizing abab on a Curve

Real numbers a,ba, b satisfy

1a22+1b23=32.\sqrt{1 - \frac{a^2}{2}} + \sqrt{1 - \frac{b^2}{3}} = \frac{3}{2}.

Find the maximum value of abab.

trigonometrySubstitutionalgebraAM-GM+1
8/10

Incircle of a Triangle Inscribed in an Ellipse

figure

The circle G:(x2)2+y2=r2G:(x-2)^2+y^2=r^2 is the incircle of triangle ABCABC, which is inscribed in the ellipse $\dfr…

plane geometrySimilar TrianglesTangent Circleconic sections+2
7/10

Dot Sums in a Disc

Points A,B,CA, B, C lie on a circle OO of radius 11, with ABAB a diameter, and PP is a point in the closed disc. Find the range of possible values of

PA\ov\overrightarrow{PA}\cdot\ov…
plane geometryExtremaCompleting the Squarevectors
7/10

Roots in the Denominator

Let a>1a > 1 and b>2b > 2. Find the minimum value of

m=(a+b)2a21+b24.m = \frac{(a+b)^2}{\sqrt{a^2-1} + \sqrt{b^2-4}}.
SubstitutionalgebraCauchy-SchwarzAM-GM+1

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