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Finding Angles Using Trigonometry Flashcards
GCSE Mathematics (Edexcel) 1MA1
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Trigonometric Ratios
The three trigonometric ratios are sine (sin), cosine (cos), and tangent (tan).
Sine Ratio
sin(angle) = opposite / hypotenuse.
Cosine Ratio
cos(angle) = adjacent / hypotenuse.
Tangent Ratio
tan(angle) = opposite / adjacent.
Finding an Angle Using Sine
To find an angle, use the inverse sine function: angle = sin⁻¹(opposite / hypotenuse).
Finding an Angle Using Cosine
To find an angle, use the inverse cosine function: angle = cos⁻¹(adjacent / hypotenuse).
Finding an Angle Using Tangent
To find an angle, use the inverse tangent function: angle = tan⁻¹(opposite / adjacent).
Right-Angled Triangle Labelling
The hypotenuse is the longest side, opposite is across from the angle, and adjacent is next to the angle.
Using a Calculator for Inverse Trigonometry
Use the sin⁻¹, cos⁻¹, or tan⁻¹ buttons on your calculator to find angles.
Rounding Angles
Angles found using trigonometry are usually rounded to 1 decimal place unless stated otherwise in the question.
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