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.

GEO-G.CO.10

Prove and apply theorems about triangles.

Example Problems

Two sides of a triangle have the following measures:
46 and 15

Find the range of possible measures for the third side:

x

Two sides of a triangle have the following measures:
50 and 44

Find the range of possible measures for the third side:

x

Two sides of a triangle have the following measures:
72 and 55

Find the range of possible measures for the third side:

x

Khan Academy Resources

Challenge problems: Inscribed angles Challenge problems: radius & tangent Inscribed angle theorem proof Intro to inverse trig functions Determining tangent lines: angles Solving for a side in right triangles with trigonometry Angles of elevation and depression Challenge problems: Inscribed shapes Determining tangent lines: lengths Trigonometric ratios in right triangles Right triangle trigonometry review Challenge problems: circumscribing shapes Special right triangles review Hypotenuse, opposite, and adjacent Solve for a side in right triangles Special right triangles Trigonometric ratios in right triangles Inscribed angles Tangents of circles problems Prove theorems using similarity Pythagorean theorem in 3D Pythagorean theorem challenge Inscribed shapes Prove triangle properties Solve for an angle in right triangles Right triangle trigonometry word problems Solving for a side in right triangles with trigonometry Trigonometric ratios in right triangles Inscribed angle theorem proof Proof: Right triangles inscribed in circles Circles glossary Angles in a triangle sum to 180° proof Triangle exterior angle example Proof: radius is perpendicular to a chord it bisects Proofs concerning isosceles triangles Proofs concerning equilateral triangles Special right triangles proof (part 2)Special right triangles proof (part 1)30-60-90 triangle example problem Proof: perpendicular radius bisects chord Exploring medial triangles Area of a regular hexagon Inscribed shapes: find inscribed angle Proving triangle medians intersect at a point Tangents of circles problem (example 1)Inscribed shapes: find diameter Inscribed angles Pythagorean theorem in 3D Proof: Radius is perpendicular to tangent line Multi-step word problem with Pythagorean theorem Inscribed shapes: angle subtended by diameter Tangents of circles problem (example 3)Proof: Segments tangent to circle from outside point are congruent Right triangle word problem Pythagorean theorem with isosceles triangle Using right triangle ratios to approximate angle measure Tangents of circles problem (example 2)

1-on-1 AI tutoring aligned to GEO-G.CO.10. 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.

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