Measurement – Right Angled Triangles By the end of this lesson you will be able to identify and calculate the following: 1. Inverse TAN (TAN -1 )
If the value of the tangent of an angle is known, the size of this angle can be found with the aid of either a scientific or a graphics calculator. Know that tan θ = , then the value of θ can be obtained by ‘undoing’ the tangent function. inverse of tangenttan −1 The inverse of tangent, denoted by tan −1 ‘undoes’ the tan, thus leaving θ on its own.
You will notice that the tangent inverse, tan −1 is written above the tan button in a different colour. When finding the inverse tangent ratio, the answer is the angle that has that ratio. In general we give angles correct to the nearest degree (whole number).
The size of any angle in a right-angled triangle can be found using the tangent ratio if the lengths of the two sides adjacent to the right angle are known. Follow these steps: 1. Label the sides of the triangle with respect to the angle to be found using the symbols O, A and H. 2. Use the tangent ratio to write a relationship between the opposite and the adjacent sides. 3. Find the size of the angle using the inverse tangent function.