Trigonometry

Right Angled Triangles |  Trigonometric Ratios |  Special Angles  |  Inverse Trigonometric Functions  |  Finding the Length of a Side of a Triangle  |  Trigonometric Identities  |  Miscellaneous  

Finding the Length of a Side of a Triangle

If the angle and the length of a side of a right angled triangle are known we can compute the lengths of the other sides.

Example 1

Suppose θ = 30º and the opposite side is O = 3. We can make use of the sin θ and Pythagoras Theorem (H² = O² + A²) or the tan θ to find the lengths of the hypotenuse and adjacent sides.

For example,

Hence

.

By Pythagoras Theorem,

.

Alternatively, we can find the adjacent side using the tangent function as follows:

.

Hence

.

Exercise 4.

Next - Trigonometric Identities

Right Angled Triangles |  Trigonometric Ratios |  Special Angles  |  Inverse Trigonometric Functions  |  Finding the Length of a Side of a Triangle  |  Trigonometric Identities  |  Miscellaneous