Right-Angled Triangles (Pythagoras & Trigonometry)Cambridge IGCSE Maths: Flashcards

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State Pythagoras' theorem.

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State Pythagoras' theorem.: $a^2 + b^2 = c^2$ , where $c$ is the hypotenuse
Which side is the hypotenuse?: The longest side of a right-angled triangle, always opposite the right angle
State the sine ratio.: $\sin\theta = \frac{\text{opposite}}{\text{hypotenuse}}$
State the cosine ratio.: $\cos\theta = \frac{\text{adjacent}}{\text{hypotenuse}}$
State the tangent ratio.: $\tan\theta = \frac{\text{opposite}}{\text{adjacent}}$
What memory aid helps recall the trig ratios?: SOH CAH TOA
A right triangle has legs 5 cm and 12 cm. Find the hypotenuse.: 13 cm ( $\sqrt{25+144}=\sqrt{169}$ )
How do you find a missing angle given two sides?: Use the inverse trig function matching the ratio, e.g. $\theta = \tan^{-1}\left(\frac{opp}{adj}\right)$
To how many decimal places should angles be given?: One decimal place
What is the perpendicular distance from a point to a line?: The shortest possible distance between the point and the line
Define angle of elevation.: The angle measured upwards from the horizontal to a point above the observer
Define angle of depression.: The angle measured downwards from the horizontal to a point below the observer
Why should you avoid rounding intermediate calculator values?: Rounding too early causes accuracy errors in the final answer
State the exact value of $\sin 30°$ .: $\frac{1}{2}$