Using the cosine ratio
I can use the cosine ratio to find the missing side or angle in a right-angled triangle.
Using the cosine ratio
I can use the cosine ratio to find the missing side or angle in a right-angled triangle.
Lesson details
Key learning points
- The cosine ratio involves the hypotenuse, adjacent and the angle.
- If you know the length of the hypotenuse and the size of the angle, you can use the cosine ratio.
- If you know the length of the adjacent and the size of the angle, you can use the cosine ratio.
- If you know the length of the hypotenuse and adjacent, you can use the cosine ratio.
Common misconception
The cosine formula is only used to find the length of a side adjacent to an angle.
The cosine formula can be used to find the length of a side adjacent to an angle. A rearrangement of the formula also allows us to find the length of the hypotenuse given the adjacent side. The arccosine function allows us to find the angle, itself.
Keywords
Hypotenuse - The hypotenuse is the side of a right-angled triangle which is opposite the right angle.
Adjacent - The adjacent side of a right-angled triangle is the side which is next to both the right angle and the marked angle.
Trigonometric functions - Trigonometric functions are commonly defined as ratios of two sides of a right-angled triangle containing the angle.
Cosine function - The cosine of an angle (cos(θ°)) is the x-coordinate of point P on the triangle formed inside the unit circle.
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
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