Show model answer and explanation
6
s=rθ.
Class 11 · Bangla Version · Mathematics
Geometry, measurement and trigonometry readiness
Use radians and vector components to relate algebra to geometry.
About this lesson and its coverage
Original Kidemy Class 11 progression. This level has its own text, examples and questions. Curriculum versions share the progression; complete board-specific coverage still needs specification matching and additional material.
Learn the idea
A radian angle satisfies arc length s=rθ. Vectors have magnitude and direction; addition combines components. The scalar product a·b=|a||b|cosθ measures alignment and can identify perpendicular vectors when nonzero vectors have product zero.
Worked example
An arc with radius 3 and angle2 radians has length6. Vectors(1,2) and (2,−1) have product0, so they are perpendicular.
- Identify the quantities and restrictions.
- Show a method with units or symbols.
- Check and explain the result.
Your written practice
Show your working on paper. Check your answer, then choose Next.
Show model answer and explanation
5
8−3.
Show model answer and explanation
13
√(25+144).
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
180°=π radians because half the circumference isπr, so s/r=π.
Use the definition of radians.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
A zero vector has no direction, and the cosine formula divides by its zero magnitude.
State the nonzero-vector condition.
Progress and browser storage
Notebook challenge, sources and further study
Apply the idea
Solve a vector perpendicularity problem and connect it to a diagram.
Review with a guardian or teacher
- Use the stated evidence or givens.
- Show reasoning rather than only a result.
- Review and explain one correction.
Keep your work on paper or in a local file. This page does not upload it or automatically grade the project.
Teacher-led lessons, schedules and prices for this outline are upcoming. You can use any starter practice above now without booking.
Your next step
Solo practice works without an account. Sign in to save a practice record to your learner profile.
Keep practising
Exact lesson links and related activities are labelled separately. Return-to-course links retain your selected learning path.