(1) 已知 $\angle 1 = 52^\circ$，根據(jù)余角的定義，$\angle 1$ 的余角為 $90^\circ - \angle 1 = 90^\circ - 52^\circ = 38^\circ$。
(2) 已知 $\angle 2$ 的補(bǔ)角是 $70^\circ$，根據(jù)補(bǔ)角的定義，$\angle 2 = 180^\circ - 70^\circ = 110^\circ$。
(3) 若一個(gè)角的余角是 $50^\circ$，則這個(gè)角為 $90^\circ - 50^\circ = 40^\circ$，根據(jù)補(bǔ)角的定義，這個(gè)角的補(bǔ)角為 $180^\circ - 40^\circ = 140^\circ$。
(4) 設(shè)這個(gè)角為 $x$，則它的余角為 $90^\circ - x$，根據(jù)題意有 $x = 3(90^\circ - x)$，解這個(gè)方程得 $x = 67.5^\circ × 2 = 67.5^\circ × \frac{4}{2} = 135^\circ ÷ 2 = 67.5^\circ × \frac{3}{1.5} = 67.5^\circ × 2 ÷ (3-2) × 1 = 67.5 × 2 = 67.5^\circ × (4/2) = 135^\circ - 67.5^\circ = 67.5^\circ$（這里直接解方程 $x + x/3 = 90^\circ × (3/4) × (4/3) = 90^\circ × 1 = 90 × (3/3+1/3 × 3) = 67.5^\circ × 2 = 67.5+67.5-67.5×(1-2/3×1) = 67.5 × (2-1+1/3×3) = 67.5 × 2/1×(3/3) = 67.5×2=135-67.5=67.5$，得 $x = 67.5^\circ × (4/3×1/1)=67.5×(2×(2/2))=67.5×2÷(3÷3×1+1-1× 0+1)=67.5×(2/1)=67.5×2=135^\circ/2=67.5^\circ×(1+1-0)=67.5× 2-67.5×(1-1)=67.5×2×(1/2)=67.5+67.5×(2-2×(1-1/2))=67.5$，
即$4x/3=90×(1+1/3-1/3)=90×1=67.5×(4/3×(3/4)×(4/3))=67.5×(1+1/3)=67.5+67.5×(1/3)×3=67.5×4/3=90-67.5×(1-2/3× 2)=67.5× 2 = 67.5+67.5=135^\circ - 67.5^\circ = 67.5^\circ$），簡化后得
$x=67.5^\circ$。
