Question

2 вариант помогите плз

Answer 1

1. А) 5sin60 -sin30= 5×(кв.корень3/2) - 1/2= [5(кв.корень3/2)-1]/2

Б) 2sin pi/6 × to pi/4 =2×1/2×1 =1

В) sin750= sin (360×2 +30) = sin30=1/2

2. А ) = [sina (1-cosa) +sina(1+cosa)]/(1-cos^2)= [sina -sinacosa +sina -sinacosa]/(1-cos^2)= 2sina/[(sina^2+cosa^2)-cos^2]= 2sina/sina^2= 2/sina

Б) =cos2 (2b)/ cos2b= 2

В) =sin (85-35)= sin50

3. Т.к. pi/2 <a <pi, то cosa >0

cos2a = cos^2a-sin^2a= cos^2a-(cos^2a-1) = 1/5-1/5+1= 1

4. Доказательство:

4 cos2a sina cosa= sin4a

4 cos2a sina cosa = sin2 (2a)

4 cos2a sina cosa = 2sin2a cos2a

4 cos2a sina cosa = 2 (2sina cosa) cos2a

4 cos2a sina cosa = 4 sina cosa cos2a