Question

Ajutor .....................

Answer 1

Se utilizeaza doua formule:
→ sin²x+cos²x=1 (formula fundamentala a trigonometriei)
→ sinx=sin(180°-x) (formula de reducere a sinusului de la cadranul II la cadranul I)

1)

sin100°=sin(180°-100°)=sin80°
sin²100°+cos²80°=sin²80°+cos²80°=1

2)

sin130°=sin(180°-130°)=sin50°
sin²130°+cos²50°=sin²50°+cos²50°=1

3) 

sin135°=sin(180°-135°)=sin45°=√2/2

4)

sin135°=sin(180°-135°)=sin45°=√2/2
sin²135°=(√2/2)²=2/4=1/2
cos45°=√2/2
cos²45°=2/4=1/2
cos²45°+sin²135°=1/2+1/2=1

5)

sin120°=sin(180°-120°)=sin60°=√3/2