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Trigonometric Foundations

Lesson · Beginner

Trigonometry

Right triangle showing angle alpha and sides AB, AC, and BC
sin⁡α=Opposite SideHypotenuse=ABBC \sin\alpha = \frac{\text{Opposite Side}}{\text{Hypotenuse}} = \frac{AB}{BC}
cos⁡α=Adjacent SideHypotenuse=ACBC \cos\alpha = \frac{\text{Adjacent Side}}{\text{Hypotenuse}} = \frac{AC}{BC}
tan⁡α=Opposite SideAdjacent Side=ABAC \tan\alpha = \frac{\text{Opposite Side}}{\text{Adjacent Side}} = \frac{AB}{AC}
cot⁡α=Adjacent SideOpposite Side=ACAB \cot\alpha = \frac{\text{Adjacent Side}}{\text{Opposite Side}} = \frac{AC}{AB}
Unit circle showing sine and cosine of alpha
Unit circle showing tangent and cotangent of alpha
Signs of sine, cosine, tangent, and cotangent in the four quadrants
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