#### How Do You Find Missing Angles by Using Trigonometry?
Geometry is a fun branch of mathematics but sometimes it can be a bit troublesome. Many students find it difficult when it comes to finding missing angles in triangles. We all know that there are three angles in triangles and their sum is equal to 180°. When two angles are given, we can find the third one by subtracting the sum of the given angles from 180°. Things get complicated when you have one or no given angle and only the sides are given.
This is where trigonometry comes in. We can solve for missing angles using trigonometric functions.
Staring with right-triangles, here we know one angle which is 90°. Now you have to find the other angles. To get started with it, you need to know that the side opposite to the 90° angle is hypotenuse, then there is the base and perpendicular.
We have three basic trigonometric functions and these are;
sinα = Opposite/Hypotenuse, cosα = Adjacent/Hypoenuse, tanα = (Opposite )/Adjacent.
You can use these to find the missing angles.
Now, if you are dealing with non-right-angle triangles you will have to use Sine and Cosine rules.
Sine Rule is used when three sides and two angles are given. The Sine Rule is;
a/sinA = b/sinB = c/sinC.
Cosine rule is used when three sides are given. The Cosine Rule is;
a^{2} =b^{2} +c^{2} -2ab cosA.
b^{2} =a^{2} +c^{2} -2ac cosB.
c^{2} =a^{2} +b^{2} -2ac cosC.

In these worksheets, students will use trigonometry to find the missing angle value of a triangle. Diagrams are included on each worksheet for students to reference. They will read the information specified about each triangle and fill in blank with the value of the missing angle. Extra paper may be required in order for students to do their calculations. This set of worksheets contains lessons, step-by-step solutions to sample problems, both simple and more complex problems, a review, and a quiz. It also includes ample worksheets for students to practice independently. Most worksheets contain between eight and ten problems. When finished with this set of worksheets, students will be able to use trigonometry to find the missing angle value. These worksheets explain how to use trigonometry to find the value of a missing angle of a triangle. Sample problems are solved and practice problems are provided.