Question

Please help... I have no clue

Answer 1

Answer:

OPTION C:  Sin C - Cos C = s - r

Step-by-step explanation:

ABC is a right angled triangle. ∠A = 90°, from the figure.

Therefore, BC = hypotenuse, say h

Now, we find the length of AB and AC.

We know that:   $\textbf{Sin A} = \frac{\textbf{opp}}{\textbf{hyp}}$

and    $\textbf{Cos A} = \frac{\textbf{adj}}{\textbf{hyp}}$

Given, Sin B = r and Cos B = s

⇒    $Sin B = r = \frac{opp}{hyp} = \frac{AC}{BC} = \frac{AC}{h}$

⇒ $\textbf{AC} = \textbf{rh}$

Hence, the length of the side AC = rh

Now, to compute the length of AB, we use Cos B.

$Cos B = s = \frac{adj}{hyp} = \frac{AB}{BC} = \frac{AB}{h}$

⇒  $\textbf{AB} = \textbf{sh}$

Hence, the length of the side AB = sh

Now, we are asked to compute Sin C - Cos C.

$Sin C = \frac{opp}{hyp}$

⇒  $Sin C = \frac{AB}{BC}$

              $= \frac{sh}{h}$

               = s

Sin C = s

$Cos C = \frac{adj}{hyp}$

$\implies Cos C = \frac{AC}{BC}$

⇒ Cos C = $\frac{rh}{h}$

Therefore, Cos C = r

So, Sin C - Cos C = s - r, which is OPTION C and is the right answer.