Is Goblins free for teachers?

Yes. Goblins offers a generous free tier that includes 1 live feedback assignment per week, insights on student mastery and replays, and the ability to upload your own content. The Max plan adds unlimited assignments, superadaptive mode, grade exports, standards growth reports, and SSO/LMS integration, with per-student pricing for schools and districts.

How does Goblins work?

Three simple steps: (1) Share an assignment from thousands of standards-aligned topics using a share code. (2) Students speak and draw their thinking naturally, and Goblins responds with Socratic questioning that sounds just like their teacher. (3) Teachers get real-time formative insights showing what students struggle with and suggestions to inform instruction.

Does Goblins prevent cheating?

Yes. Goblins uses a purpose-trained AI model that evaluates cheating signals in real time. It can detect when students are copying answers, using external tools inappropriately, or not genuinely working through problems. Copy-pasting answers is also blocked.

Can I use my own voice with Goblins?

Yes. Teachers can record their voice and take a selfie to create a custom 3D avatar in about 30 seconds. Students then hear help in their own teacher's voice and see a familiar face, making the experience more personal and effective.

What math levels does Goblins cover?

Goblins covers math from Grade 5 through AP Calculus, including thousands of standards-aligned topics. Teachers can also upload their own content for custom assignments at any level.

Is Goblins FERPA compliant?

Yes. Goblins is FERPA and state compliant. Student data privacy and security are a top priority.

Does Goblins support English Language Learners?

Yes. Goblins supports 30+ languages so teachers don't have to translate every worksheet. It is especially helpful for ELL students who need accessible math instruction in their native language.

HS.G.1.j

Identify, describe, apply, and reason through properties of central angles, inscribed angles, angles formed by intersecting chords, secants, and/or tangents to find the measures of angles related to the circle, arc lengths, and areas of sectors.

Example Problems

An arc subtends a central angle of

\frac{7}{6}\pi

radians. What fraction of the circumference is the arc?

An arc subtends a central angle of

\frac{7}{4}\pi

radians. What fraction of the circumference is the arc?

An arc subtends a central angle of

\frac{11}{6}\pi

radians. What fraction of the circumference is the arc?

Khan Academy Resources

Challenge problems: Inscribed angles Inscribed angle theorem proof Challenge problems: Arc length 1 Determining tangent lines: angles Challenge problems: Arc length 2 Challenge problems: Inscribed shapes Determining tangent lines: lengths Challenge problems: Arc length (radians) 2 Challenge problems: Arc length (radians) 1 Inscribed angles Arc length Area of a sector Tangents of circles problems Inscribed shapes Radians & arc length Inscribed angle theorem proof Proof: Right triangles inscribed in circles Proof: radius is perpendicular to a chord it bisects Proof: perpendicular radius bisects chord Geometry proof problem: squared circle Arc length from subtended angle: radians Inscribed shapes: find inscribed angle Tangents of circles problem (example 1)Solving inscribed quadrilaterals Area of a sector Inscribed angles Proof: Radius is perpendicular to tangent line Inscribed shapes: angle subtended by diameter Radians as ratio of arc length to radius Subtended angle from arc length Arc length from subtended angle Arc length as fraction of circumference Tangents of circles problem (example 2)

1-on-1 AI tutoring aligned to HS.G.1.j. Instant help for students, real-time insights for teachers.

Used in classrooms by 100,000+ students at Baltimore County, Plano ISD, Deer Valley USD, KIPP, and districts nationwide.

Free for teachers, forever →