Может кто-то знает , нужно написать письмо
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Сначала формулы . затем формулы двойного угла sin2α=2sinαcosα cos2α=cos²α-sin²α=cos²α-(1-cos²α)=2cos²α-1⇒  2cos²α=1+cos2α cos2α=cos²α-sin²α=1-sin²α-sin²α=1-2sin²α⇒  2sin²α=1-cos2α а) сos75°cos105°=cos(90°-15°)·cos(90°+15°)== sin15°(-sin15°)=-sin²15°=-(1-cos30°)/2=(cos30°-1)/2= ((√3/2)-1)/2=0,25√3-0,5б) sin75°sin15°=°sin(90°-15°)sin15°=cos15° sin15°=sin30°/2=1/4=0,25в) sin105°cos15°=sin(180°-75°)cos15°=sin75°cos15°=sin(90°-15°)cos15°=cos15°cos15°=(1+cos30°)/2=(1+(√3/2))/2=0,5 +0,25√3 2 способ формулы cosα·cosβ=0,5cos(α-β)+0,5cos(α+β) sinα·sinβ=0,5cos(α-β)-0,5cos(α+β) sinα·cosβ=0,5sin(α+β)+0,5sin(α-β) а) сos75°cos105°=0,5cos(75°-105°)+0,5cos(75°+105°)=0,5cos(-30°)+0,5 cos180°==0,5· √3/2+0,5·(-1)=0,25√3-0,5б) sin75°sin15°=0,5cos(75°-15°)-0,5cos(75°+15° )=0,5cos60°-0,5 cos90°=0,5·0,5=0,25в) sin105°cos15°=0,5sin(105°+15°)+0,5sin(105°-15°)= =0,5sin120°+0,5sin90°==0,5 sin(180°-60°)+0,5·1=0,5 sin 60°+0,5=0,25√3+0,5

1. It has been raining all day long.

2. She has wanted this job for a long time.

3. They have been learning English for 2 years.

4. They have been owning this house for many years

5. He has been working hard this month.

6. He has been seeing her a lot lately.

7. I have known her for ages.

8. She has heard it several times.

9. They are having regular meetings lately.

10. The cook has been tasting the dishes since 2 o’clock.

Work in pairs. Most of the sentences below have mistakes. Find and correct them. Example:

0 growing With all the rain, the plants have been grown steadily.

1. John has been learning English since June.

2. She has been owning the house for two years.

3. He’s been reading the book for a long time.

4. We’ve lived here since 2003.

5. They have known it since morning.

6. Jane has always being very popular.

7. It has been raining for the second hour.

8. He hasn’t heard about her lately

9. She has been coming to our place many times.

10. He has read a lot before the exam.

Объяснение: