Understanding the inverse cosine or arccos function Practice this lesson yourself on KhanAcademy.org right now: https://www.khanacademy.org/math/trigonometry/unit-circle-trig-func/inverse_trig_functions/e/inverse_trig_functions?utm_source=YT&utm_medium=Desc&utm_campaign=Trigonometry Watch the next lesson: https://www.khanacademy.org/math/trigonometry/unit-circle-trig-func/inverse_trig_functions/v/inverse-trig-functions-arctan?utm_source=YT&utm_medium=Desc&utm_campaign=Trigonometry Missed the previous lesson? https://www.khanacademy.org/math/trigonometry/unit-circle-trig-func/inverse_trig_functions/v/inverse-trig-functions-arcsin?utm_source=YT&utm_medium=Desc&utm_campaign=Trigonometry ... https://www.youtube.com/watch?v=eTDaJ4ebK28 Note: All Khan Academy content is available for free at (www.khanacademy.org)

More free lessons at: http://www.khanacademy.org/video?v=rai9hJOGJLE ... https://www.youtube.com/watch?v=rai9hJOGJLE Note: All Khan Academy content is available for free at (www.khanacademy.org)

Sal answers questions for School Leadership Briefing ... https://www.youtube.com/watch?v=epQlOmZ0Kzs Note: All Khan Academy content is available for free at (www.khanacademy.org)

Comparing fractions visually with pies Practice this lesson yourself on KhanAcademy.org right now: https://www.khanacademy.org/math/cc-fourth-grade-math/cc-4th-fractions-topic/cc-4th-comparing-fractions-visually/e/visually-comparing-fractions?utm_source=YT&utm_medium=Desc&utm_campaign=4thgrade Watch the next lesson: https://www.khanacademy.org/math/cc-fourth-grade-math/cc-4th-fractions-topic/cc-4th-comparing-fractions/v/comparing-fractions-with-different-denominators?utm_source=YT&utm_medium=Desc&utm_campaign=4thgrade Missed the previous lesson? https://www.khanacademy.org/math/cc-fourth-grade-math/cc-4th-fractions-topic/cc-4th-comparing-fractions-visually/v/comparing-fractions-on-a-number-line?utm_source=YT&utm_medium=Desc&utm_campaign=4thgrade Grade 4th on Khan Academy: 4th grade is the time to start really fine-tuning your arithmetic skills. Not only will you be a multi-digit addition and subtraction rockstar, but you'll extend the multiplication and division that you started in 3rd grade to several digits. You'll also discover that you sometimes have something left over (called a "remainder") when you divide. In 3rd grade you learned what a fraction is. Now you'll start adding, subtracting, multiplying, and comparing them. You'll also see how they relate to decimals. On other fronts, you'll learn how to convert between different units (which is super important when comparing the size and speed of robot unicorns in different countries) and continue your journey thinking about various shapes in two dimensions. Some of the foundational concepts of geometry (like lines, rays and angles) also get introduced. As always, we'll round this out with a healthy dose of applied word problems and explorations of number patterns and properties (including the ideas of factors, multiples and prime numbers). The fun must not stop! (Content was selected for this grade level based on a typical curriculum in the United States.) ... https://www.youtube.com/watch?v=uCtXyhepAmQ Note: All Khan Academy content is available for free at (www.khanacademy.org)