Exercises: Sine, Cosine and Tangent on a right triangle

A triangle with a right angle at $C$ , with side $b = 113 m$ has an angle $α = 39^{\circ}$ . First make a sketch and then calculate all the missing sides and the other angle $β$ .

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$\cos (39 °)$	$=$	$\frac{113 m}{c}$	$\cdot c$
	↓	Get c on one side
$c \cdot \cos (39 °)$	$=$	$113 m$	$: \cos (39 °)$
$c$	$=$	$\frac{113 m}{\cos (39 °)}$
$c$	$=$	$145 m$

$β + 90 ° + 39 °$	$=$	$180 °$
$β$	$=$	$180 ° - 90 ° - 39 °$
$β$	$=$	$51 °$

$\sin (39 °)$	$=$	$\frac{a}{145 m}$	$\cdot 145 m$
$a$	$=$	$\sin (39 °) \cdot 145 m$
$a$	$=$	$91 m$

Exercises: Sine, Cosine and Tangent on a right triangle

1. Make a sketch

2. Calculate