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No. 4 → A

Q(0,5) → r = √(x² + y²) = √(0² + 5²) = 5

sin a = y/r = 5/5 = 1

No. 5 → A

R(a,24)

O(0,0)

OR² = x² + y²

25² = a² + 24²

a² = 25² – 24²

a² = (25 – 24)(25 + 24)

a = 7 atau a = -7

dg sb x positif → a = 7

sec alpha = OR/a = 25/7

No. 6 → C

T(a,30)

sin alpha = 15/17

30/OT = 15/17

OT = 34

OT² = x² + y²

34² = a² + 30²

a² = 34² – 30²

a = √((34 + 30)(34 – 30))

a = 8 × 2

a = 16