How to Find an Angle in a Right Triangle Given All Three Sides
Learn how to calculate an angle in a right triangle using all three sides with the cosine rule and arccosine function.
90 views
To find an angle in a right triangle when you know all three sides, use the cosine rule. For angle θ, the formula is θ = arccos((adjacent side) / hypotenuse). For angle Φ, use Φ = arccos((opposite side) / hypotenuse). Use a calculator to find the arccosine value.
FAQs & Answers
- What formula is used to find an angle in a right triangle when all sides are known? You use the cosine rule, specifically the arccosine function of the adjacent or opposite side divided by the hypotenuse.
- Can I use the sine or tangent functions if I know all three sides? While sine and tangent are useful when certain sides or angles are known, the cosine rule with arccosine is best when all three sides are given.
- How do I calculate the arccosine on my calculator? Use the inverse cosine (cos⁻¹ or arccos) function on your scientific calculator after inputting the ratio of the known side over the hypotenuse.