1.Sa se calculeze sin75°+sin15°
2.Sa arate ca 2(sin75°-sin15°)=√2
3.Sa se caluculeze cos75°-cos15°
4.Sa se calculeze sin75°·cos15°
5.Sa se calculeze tg2x,stiind ca ctg x=3
6.Sa se calculeze sin  \frac{7 \pi }{4}
7.Sa se calculeze cos  \frac{7 \pi }{12}
8.Stiind ca sin a=  \frac{1}{3} sa se calculeze cos2a
9.Fie a∈ ( \pi , \frac{3 \pi }{2} ) astfel incat cos a = ⁻  \frac{5}{13} .Sa se calculeze sin a
10.Sa se calculeze tg ( \frac{ \pi }{2} - arctg \frac{1}{2} )
11.Fie x∈R,astfel incat tg²=6.Sa se calculeze cos²x

1

Răspunsuri

2014-06-12T09:25:29+03:00
1....sin75°+sin15°=sin 90de grade
2....
2(sin75°-sin15°)=√2
      2*sin 75 -2*sin 15=
√2
      sin150-sin30=√2
      sin120=√2
      sin=120√2
Celelalte nu le stiu......