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Master Angles in a Circle: Formulas, Rules, and Examples

Grade 12 Math: Master Advanced Concepts & Skills

Geometric constructions

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Classifying triangles

Isosceles and equilateral triangles

Conics - Parabola

Conics - Circle

Conics - Ellipse

Conics - Hyperbola

Parallel and perpendicular lines

Pairs of lines and angles

Parallel lines and transversals

Parallel line proofs

Perpendicular line proofs

Circle geometry

Angles in a circle

Circles and circumference

Circle properties

Arcs of a circle

Areas and sectors of circles

Transformations of 2D shapes

Line symmetry

Rotational symmetry and transformations

Enlargements and reductions with scale factors

Scale diagrams

Similar triangles

Similar polygons

Non-Euclidean geometries

Combining transformations of functions

Surface area of 3-dimensional shapes

Transformations of functions: Horizontal translations

Transformations of functions: Vertical translations

Reflection across the y-axis: y = f(-x)

Reflection across the x-axis: y = -f(x)

We&apos;ve got you covered with our complete help for Grade 12 math, whether it&apos;s Ontario curriculum, <a href="https://www.alberta.ca/writing-diploma-exams.aspx">Diploma exam</a> (Alberta), <a href="http://www.edu.gov.mb.ca/k12/assess/tests/index.html">Provincial test</a> (Manitoba) or <a href="https://www.saskatchewan.ca/residents/education-and-learning/departmental-exams">Departmental exam</a> (Saskatchewan).

Aligned with your class or textbook, you will get grade 12 math help on topics like Trigonometric identities, Vectors, Permutations and Combinations, Matrices, Polynomial functions and so many more. Learn the concepts with our video tutorials that show you step-by-step solutions to even the hardest grade 12 math questions. Then, strengthen your understanding with tons of grade 12 math practice. 

All our lessons are taught by experienced Grade 12 math teachers. Let&apos;s finish your homework in no time, and ACE that final.

Geometry 12

math

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Intro

- Hi, welcome to this question right here. So, in the following diagram which is here, the radius of the triangle is 24 centimeters, right? And we know the angle B, D, and C. That's this angle right here, is 75 degrees. So, we're trying to figure out the angle BAC, which is right over here. So, that's the missing angle that you're trying to figure out, okay? 
Now, there's a relationship between this angle and this angle. Now, the angle 75 is called the central angle. The central angle is called the C, for example, okay? 
And the inscribed angle of that central angle is only just half of that, okay? So, it's equal to the inscribed angle but you need to put a two times right there, okay? 
So, basically the central angle is double, double of the inscribed angle. Now, how do you know that one is really an inscribed while the other is the center? Well, the central angle is always from a point and then the other point, and they form with the center line, okay? The center point, okay? So, this is your central angle right here. Now, if you start and finish with the same points, which is B and C, and you form any triangle around your circle right here, those are called your inscribed angles, okay? Or they have the same arc lengths. You can actually look at the arc lengths right here. This is the arc length of the triangles, right? 
So, as long as they share the same arc length. Doesn't have to start from here to here. It could be somewhere else. As long as the arc length, the A-R-C, is the same. Therefore, this equation right here will exist, okay? The central angle is the double of the inscribed angle. So, if that's 75 over here, then, basically it's just two times the missing angle. Which is, let me put down. . . 
75 degrees and there's your two theta that's missing, okay? So, just grab your calculator and take the 75 divided by two, you get yourself the angle, which is this one right here, the BAC will just be 37.5 degrees. And that's your final answer for this question. Thanks for watching.

In a circle, chords, angles, inscribed angles and arc length all have special relationships with each other. This lesson focuses on exploring the relationships among inscribed angles in a circle as well as those of inscribed angle and central angle with the same arc. We will make use of the relationships to solve related questions in this lesson.  

Using formulas to find angles in a circle

Central angles and proofs

Inscribed angles and proofs