Trigonometry · Second Year
Trigonometry
Second Year · SOH CAH TOA · Tap NEXT to begin
Section 1 of 2
SOH CAH TOA
In a right-angled triangle, name the sides from the angle $A$, then use the ratios.
The three ratios
$\sin A = \dfrac{\text{opp}}{\text{hyp}}$ $\cos A = \dfrac{\text{adj}}{\text{hyp}}$ $\tan A = \dfrac{\text{opp}}{\text{adj}}$.
Section 2 of 2
Finding a Side
Now you try
You try
Find $x$ if $\sin 30^{\circ} = \dfrac{x}{10}$.
Pen and paper out — try it before you reveal.
$x = 10\sin 30$
$x = 5$
$x = 5$
You try
A right triangle has opposite $5$ and adjacent $7$. Find the angle $A$ (1 d.p.).
Pen and paper out — try it before you reveal.
$\tan A = \dfrac{5}{7} \Rightarrow A = \tan^{-1}(0.714)$
$A = 35.5^{\circ}$
$A = 35.5^{\circ}$
That’s Trigonometry.
SOH CAH TOA to find a side or an angle in a right-angled triangle.