Yang (ii) Apa jawabannya? Dan mengapa?

karena ∆PQR segitiga siku-siku sama kaki maka <PRQ = <QPR = 45°
PQ = QR = 1, QS = x => PS = (1 - x)
RS = √(x^2 + 1)
RP = √(1^2 + 1^2) = √2
pada ∆SQR => cos o = QR/RS = 1/√(x^2 + 1)
pada ∆PSR => cos o = (RP^2 + RS^2 - PS^2)/(2.RP.RS)
cos o = (√2^2 + √(x^2 + 1)^2 - (1 - x)^2) / (2 . √2 . √(x^2 + 1))
1/√(x^2 + 1) = (2 + x^2 + 1 - (1 - 2x + x^2) / (2√2.√(x^2 + 1))
1/1 = (2 + 2x)/(2√2)
2√2 = 2 + 2x
√2 = 1 + x
x = √2 - 1 ............ (kedua ruas dikali √2 + 1)
x (√2 + 1) = (√2 - 1) (√2 + 1)
x√2 + x = 2 - 1
x√2 = 1 - x

<PRQ = 45° => <QRS = 22 1/2°
pada ∆QRS => Tan o = QS/RQ
Tan 22 1/2° = x/1
Tan 22 1/2° = √2 - 1