Unit Circle With Tangent – Definition With Examples
Updated on January 13, 2024
Welcome to another exciting journey with Brighterly – the home of fun, engaging, and insightful math learning for children. Today, we’re setting sail into the vast ocean of mathematics to discover and explore the fascinating concept of the unit circle and tangent. We know that the idea of unit circles and tangents might seem complex at first, especially if you’re just stepping into the world of trigonometry. But remember, at Brighterly, we always ensure learning is an adventure!
Every twist and turn of the unit circle, every rise and fall of the tangent line, offers a chance to better understand how these mathematical constructs elegantly intertwine. We’ll venture from definitions to equations, stopping at key properties, and concluding with practice problems to cement your newfound knowledge. Along the way, you’ll see how these mathematical treasures illuminate paths to countless other math topics. So, let’s hoist the anchor and set sail into this intriguing voyage!
What Is the Unit Circle and Tangent?
A unit circle is a circle with a radius of one unit, typically centered at the origin (0,0) of a coordinate plane. On the other hand, tangent in trigonometry refers to a specific function of an angle, often represented as tan(θ). But how do these two seemingly disparate concepts intertwine? Let’s dive deeper to understand.
Definition of the Unit Circle
A unit circle is defined as a circle with a radius of exactly one unit. It’s typically placed on a coordinate plane with its center at the origin, or the point (0,0). Think of the unit circle as the perfect circle – not too large, not too small, just right. It’s the Goldilocks of the circle family, and its size makes it an essential tool for understanding angles, trigonometry, and the relationship between different trigonometric functions.
Definition of Tangent
Tangent, or tan(θ), is one of the primary functions in trigonometry, along with sine and cosine. Specifically, tangent is the ratio of the length of the side opposite an angle to the length of the side adjacent to it in a rightangled triangle. However, in the context of the unit circle, the tangent of an angle is the ycoordinate divided by the xcoordinate of the point on the unit circle corresponding to that angle.
Properties of the Unit Circle and Tangent
Trigonometric functions and the unit circle share intriguing properties that make them cornerstones of mathematics.
Properties of the Unit Circle
The unit circle’s properties are simple yet profound. Every point (x, y) on the unit circle can be expressed in terms of cosine and sine of an angle θ. The xcoordinate is the cosine of that angle (cos θ), and the ycoordinate is the sine of that angle (sin θ). Moreover, the equation of a unit circle is x² + y² = 1, reinforcing the radius of 1.
Properties of Tangent
The tangent function exhibits periodic behavior, with a period of π (or 180 degrees), and it is undefined at odd multiples of π/2 (or 90 degrees). Additionally, the tangent of an angle in the unit circle equals the slope of the line passing through the origin and the point corresponding to the angle on the unit circle.
Relationship Between the Unit Circle and Tangent
The unit circle and tangent are intertwined in a beautiful, mathematical dance. On the unit circle, an angle’s tangent value is the slope of the line from the origin (0,0) to the point on the circle corresponding to the angle. When the line is vertical (or undefined), it aligns with the tangent’s behavior, which is also undefined at specific angles.
Equations of the Unit Circle and Tangent
Like the steps to a dance, these equations guide us through the intricate relationship between the unit circle and tangent.
Writing Equations of the Unit Circle
The equation of a unit circle is simple: x² + y² = 1. This equation tells us that any point (x, y) on the unit circle is a solution to this equation.
Writing Equations of Tangent
Given an angle θ, the tangent equation is: tan(θ) = sin(θ) / cos(θ). In the context of the unit circle, where the point on the circle is (cos θ, sin θ), the tangent of the angle equals the ycoordinate (sin θ) divided by the xcoordinate (cos θ).
Practice Problems on the Unit Circle and Tangent
Applying your knowledge is key to mastering any concept. Let’s dive into some practice problems that explore the unit circle and tangent.

Problem: Find the coordinates (cos θ, sin θ) of an angle θ = 60° on the unit circle.
Solution: Using the unit circle, we find that at 60°, cos θ = 1/2 and sin θ = √3/2. So, the coordinates are (1/2, √3/2).

Problem: What is the tangent of an angle θ = 45° in the context of the unit circle?
Solution: At 45° on the unit circle, cos θ = sin θ = √2/2. Thus, tan(45°) = sin(45°) / cos(45°) = 1.

Problem: Find the value of θ for which tan(θ) is undefined.
Solution: Tangent is undefined where the xcoordinate (cos θ) on the unit circle equals zero, i.e., at odd multiples of π/2 (or 90°). Therefore, θ could be π/2, 3π/2, 5π/2, and so on.

Problem: Given the coordinates (1/2, √3/2) on the unit circle, find the corresponding angle θ.
Solution: If cos θ = 1/2 and sin θ = √3/2, referring to the unit circle tells us that these coordinates correspond to an angle θ of 60°.

Problem: Determine the tangent of an angle θ = 30° in the context of the unit circle.
Solution: At 30° on the unit circle, cos θ = √3/2, and sin θ = 1/2. Therefore, tan(30°) = sin(30°) / cos(30°) = 1/√3.
Remember, mastering these concepts takes time and practice. Keep going through these problems, and soon you’ll be able to tackle any question involving the unit circle and tangent!
Conclusion
And there you have it, a detailed exploration of the unit circle and tangent, courtesy of Brighterly. These are more than just abstract mathematical concepts; they are a gateway to understanding the world around us. From the orbits of planets to the architecture of buildings, unit circles and tangents, like much of mathematics, underpin our everyday reality.
At Brighterly, we believe in making complex concepts like these not just understandable but enjoyable. Math is not just numbers and equations; it’s a language that helps us decipher the mysteries of the universe, and we hope you’ve enjoyed reading this as much as we enjoyed putting it together for you.
Remember, mathematics is a journey of discovery, and every new concept you learn is another step towards understanding this vast, beautiful universe of numbers and shapes. Keep practicing, stay curious, and let your knowledge shine ever brighter!
Frequently Asked Questions on the Unit Circle and Tangent

Why is the unit circle important in trigonometry?
The unit circle plays a crucial role in trigonometry because it creates a framework that unifies trigonometric functions, enabling a geometric interpretation of these functions. In the unit circle, every point corresponds to an angle, and the coordinates of that point (cos θ, sin θ) represent the cosine and sine of that angle, respectively. This representation simplifies the understanding of sine, cosine, and tangent in relation to angles and real numbers, hence its significant role in trigonometry.

Where is tangent undefined on the unit circle?
In the context of the unit circle, the tangent function is undefined at angles where the xcoordinate, or the cosine of the angle, is zero. These occur at odd multiples of π/2 (or 90 degrees). For example, at π/2 and 3π/2, the xcoordinate is zero. Hence, tan(θ) = sin(θ) / cos(θ) is undefined, as we would be dividing by zero.

How is the tangent related to the unit circle?
In the unit circle, the tangent of an angle represents the slope of the line from the origin (0,0) to the point on the circle corresponding to that angle. This visual representation helps provide an intuitive understanding of the tangent function. Moreover, the tangent of an angle is defined as the ratio of the ycoordinate (sin θ) to the xcoordinate (cos θ) of that point on the unit circle. Therefore, the unit circle and the tangent function are interlinked, enhancing our understanding of trigonometry and geometry.