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★ 8/10

An Incenter Times a Foot

The point PP lies on the right branch of x2−y23=1x^2 - \dfrac{y^2}{3} = 1 with foci F1,F2F_1, F_2, and ∣PF2∣=2|PF_2| = 2. Let II be the incenter of △PF1F2\triangle PF_1F_2, OO the origin, and MM…

plane geometryReflectionTangent Circleconic sections+1
★ 7/10

Maximum Distance of a Sliding Triangle's Vertex

figure

In right triangle ABCABC, ∠C=90∘\angle C = 90^\circ, AC=4AC = 4, and BC=2BC = 2. Points AA and CC lie on the xx-axis a…

plane geometrytrigonometryanalytic geometryTriangle Geometry
★ 8/10

A Centroid Right-Angle Relation

Let GG be the centroid of △ABC\triangle ABC with AG⊥BGAG\perp BG, and

1tan⁡A+1tan⁡B=λtan⁡C.\frac 1{\tan A}+\frac 1{\tan B}=\frac{\lambda}{\tan C}.

Find λ\lambda.

plane geometrytrigonometryLaw of CosinesTriangle Geometry+1
★ 7/10

Four Roots on a Circle

The real-coefficient equations

x2−2x+2=0andx2+2mx+1=0x^2 - 2x + 2 = 0 \qquad\text{and}\qquad x^2 + 2mx + 1 = 0

have four distinct roots whose points in the complex plane are concyclic. Find the ra…

complex numbersQuadratic EquationsCirclesCasework
★ 7/10

A Monotone Decrease Constraint

Let m,n⩾0m, n \geqslant 0, and suppose

f(x)=12(m−2)x2+(n−8)x+1f(x) = \frac{1}{2}(m-2)x^2 + (n-8)x + 1

is decreasing on the interval [12,2]\left[\dfrac{1}{2}, 2\right]. Find the maximum value of mnmn.

functionsLinear ProgrammingMonotonicityAM-GM+1
★ 7/10

Forced by an Identity

In △ABC\triangle ABC,

3sin⁡2B+7sin⁡2C=2sin⁡Asin⁡Bsin⁡C+2sin⁡2A.3\sin^2 B + 7\sin^2 C = 2\sin A\sin B\sin C + 2\sin^2 A.

Find sin⁡(A+π4)\sin\left(A + \dfrac{\pi}{4}\right).

Law of SinestrigonometryLaw of CosinesAM-GM+1
★ 8/10

A Fractional-Part Membership Rule

A strictly increasing sequence of positive reals {xn}\{x_n\} has the property: x∈{xn}x \in \{x_n\} iff x+{x}2x + \{x\}^2 is an integer, where {x}\{x\} is the fractional part of xx. Find …

Quadratic Equationsnumber theoryalgebrasequences+1
★ 7/10

A Lemniscate Checklist

The curve CC (a lemniscate) is the locus of points whose distances to F1(−a,0)F_1(-a, 0) and F2(a,0)F_2(a, 0) have product a2a^2. Determine, with proof, which of the following are true:

1…

ExtremaSubstitutionanalytic geometry
★ 7/10

A Tangent Simplification

Simplify and evaluate:

tan⁡96∘−tan⁡12∘(1+1sin⁡6∘)1+tan⁡96∘tan⁡12∘(1+1sin⁡6∘).\frac{\tan 96^\circ - \tan 12^\circ\left(1 + \dfrac{1}{\sin 6^\circ}\right)}{1 + \tan 96^\circ \tan 12^\circ\left(1 + \dfrac{1}{\sin 6^\circ}\right)}.
trigonometryTrigonometric Identities
★ 7/10

Three Circles and a Minimum

Real numbers x,y,tx, y, t satisfy

x2+y2=1,(x−t)2+y2=5.x^2 + y^2 = 1, \qquad (x-t)^2 + y^2 = 5.

Find the minimum value of x2+(y−2t)2x^2 + (y - 2t)^2.

algebrainequality
★ 7/10

A Boundary Critical Point

Let

f(x)=x2−2ax+4(a−1)ln⁡(x+1),f(x) = x^2 - 2ax + 4(a-1)\ln(x+1),

where the real number a<3a < 3.

1. Is x=1x = 1 a critical (extremum) point of f(x)f(x)? Explain. 2. If f(x)⩽0f(x) \leqslant 0 on the interval …

functionsExtremacalculusMonotonicity+1
★ 8/10

A Chord of Length Two

The ellipse Γ:x2a2+y2b2=1\Gamma:\dfrac{x^2}{a^2}+\dfrac{y^2}{b^2}=1 (a>b>0a>b>0) passes through the point P(0,3)P(0,\sqrt 3); its left and right vertices are A1A_1, A2A_2, and the product of the slo…

Substitutionconic sectionsSymmetry

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