Gunakan konsep rumus cosinus jumlah dua sudut, perbandingan sisi trigonometri, relasi sudut
.

Ingat kembali nilai trigonometri sudut istimewa
dan
.

Diketahui segitiga
adalah segitiga sama kaki dengan
dan
.
*Terlebih dahulu tentukan sisi depan dan sisi miring dari nilai sinus yang diketahui.

Diperoleh sisi depan dan sisi miring sudut
adalah
dan
.
Agar lebih mudah ilustrasikan terlebih dahulu informasi yang diketahui menjadi sebagai berikut.

a. Menentukan batas nilai 
Sudut
harus berada antara
dan
untuk menjadi segitiga sama kaki, sehingga diperoleh sebagai berikut.

Jadi, diperoleh bahwa batas nilai
adalah
.
b. Menentukan
.
Karena segitiga tersebut sama kaki, maka besar
, sehingga diperoleh:

Jadi, diperoleh nilai
.
c. Menentukan 
Terlebih dahulu tentukan sisi samping sudut
dengan menggunakan teorema Pythagoras, diperoleh sebagai berikut.

Diperoleh sisi samping sudut
adalah
, sehingga nilai
dapat dihitung sebagai berikut.

Diperoleh nilai 
d. Menentukan 
Karena segitiga tersebut sama kaki, maka besar
, sehingga diperoleh:

Jadi, diperoleh nilai
.
e. Menentukan 
Ingat bahwa jumlah sudut dalam segitiga adalah
, sehingga diperoleh sebagai berikut.

Untuk menentukan nilai
dapat diperoleh dengan cara.

Sehingga untuk menentukan nilai
dapat diperoleh dengan menghitung nilai
.

Jadi, diperoleh nilai
.
f. Menentukan 
Untuk menentukan nilai
dapat diperoleh dengan cara.

Sehingga untuk menentukan nilai
dapat diperoleh dengan menghitung nilai
.

Jadi, diperoleh nilai
.