Similar triangles · Geometric proofs · Right and non-right trigonometry
Change the scale factor without changing the angle measures.
∠A = ∠D, ∠B = ∠E, and ∠C = ∠F.
AB ↔ DE, BC ↔ EF, AC ↔ DF.
Each enlarged side is multiplied by the same scale factor. All angles remain equal.
Use facts and valid reasons to justify similarity.
A proof must use enough information. SSA alone does not establish triangle similarity.
See how the sides change as you adjust the angle.
Sine = opposite ÷ hypotenuse
Cosine = adjacent ÷ hypotenuse
Tangent = opposite ÷ adjacent
Use inverse trigonometry to find an unknown acute angle from two known sides.
Choose the sine rule or cosine rule.
Use the cosine rule for SAS or SSS cases. Use the sine rule when you know a side and its opposite angle, together with another suitable side or angle. Watch for an ambiguous SSA case.
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Numerical answers are rounded to one decimal place unless otherwise indicated.
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