Question

notes for trigonometry
trig functions:
sine cosine tangent
all trig functions are used for right triangles only. each one is a proportion and when working the problem should be cross multiplied and solved.
sine x°=
cosine x°=
tangent x°=
if you use a different angle, then the adjacent and opposite legs reverse. you never use the right angle for trig and the hypotenuse never changes position.
mnemonic for remember the trig functions
sohcahtoa
s-
o-
h-
c-
a-
h-
t-
o-
a-
there are two types of trig problems. one you find the missing side, the other your find the missing angle. each one is worked a different way, so look at the examples carefully.
example 1 using
find x.
12
x
21°

Explanation:

Step1: 확인할 삼각함수 식 결정

주어진 각도 $21^{\circ}$ 에 대한 빗변 $12$ 과 빗변에 대해 인접하지 않은 변 $x$ 가 주어져 있으므로 $\sin$ 함수를 사용합니다. $\sin\theta=\frac{\text{빗변에 대해 반대편 변}}{\text{빗변}}$ 입니다.

Step2: 식에 값 대입

$\sin21^{\circ}=\frac{x}{12}$ 입니다.

Step3: $x$ 값 구하기

$x = 12\times\sin21^{\circ}$ 이며, $\sin21^{\circ}\approx0.3584$ 이므로 $x\approx12\times0.3584 = 4.3008$.

Answer:

$x\approx4.30$