tolong yaaaa nomor 18 dan abaikan coretannya hehehe

Mapel : Matematika
Kelas : X SMA
Bab : Trigonometri

Pembahasan :
Aturan Cosinus

Cos < PRQ = (4² + 5² - 7²)/2(4)(5)
Cos < PRQ = (16 + 25 - 49)/40
Cos < PRQ = -8/40
Cos < PRQ = -1/5

Tan < PRQ = [√(5² - (-1)²]/-1
Tan < PRQ = [√(25 - 1)]/-1
Tan < PRQ = - √24

Trigonometri


Pakai aturan cosinus
PQ² = PR² + QR² - 2 . PR . QR . cos R
7² = 4² + 5² - 2 . 4 . 5 . cos R
49 = 16 + 25 - 40 cos R
40cosR = 16+25-49
cos R = -8/40 = -1/5

krn cos negatif , brrti ad di kuadran II atau III. Tapi ga mungkin di kuadran 3, krn max segitiga sudutnya 180°

kuadran II tan -

cos R = -1/5
sa/mi = -1/5

sa = -1
mi = 5

de = √5² - (-1)²
= √25 - 1
= √24

tan R = de/sa
= √24 / -1
= -√24

B