Question

Simplify the expression: 1) sin 20° cos 40° + cos 20° sin 40°; 2) sin 45° cos 15° + cos 45° sin 15°; 3) cos 12° cos 18° – sin 12° sin 18°; 4) cos 98° cos 8° – sin 98° sin 8°; 5) tg 22 tg 23 1 tg 22 tg 23 ; 6) tg 45 tg 15 1 tg 15 tg 45 .​

Answer 1

Answer:

1. 0.86602540....

2. 0.8662540....

3. 0.86602540.....

4. -0. 27563735......

5. tg^22 , tg^23 , 506t^2g^2

6. 675t^2g^2 , 675t^2g^2