Trigonometrik funksiyalarning qo‘shish teoremalari. Teorema. Ikki argument yig‘indisi (ayirmasi) ning kosinusi argumentlar kosinuslarini ko‘paytmasidan shu argumentlar sinuslari ko‘paytmasini ayirilganiga (qo‘shilganiga) teng boMadi: cos(a±p)= cos a cos P +sin a sin p Teorema. Ikki argument yig‘indisi (ayirmasi) ning sinusi birinchi argument sinusini ikkinchi argument kosinusiga ko‘paytmasiga birinchi argument kosinusini ikkinchi argument sinusiga ko‘paytmasini qo‘shilganiga (ayrilganiga) teng boTadi: sin(a ± p) = sin a cos P ± cos a sin p
Teorema. a va P argumentlarning har qanday qiymatida:
tg(a ± P)
tga + rgp 1 + tgatgft
1-misol: sin 75° ni hisoblang. Yechish: sin 75° = sin(45° + 30°) = sin 45° • cos 30° + cos 45° - sin 30°
42 V3 +V2 J_
2222
2-misol: Yechish:
sm 105° ni hisoblang.
sin 105° = sin(60° + 45°) = sin 60° • cos 45° + cos 60° • sin 45° = = £Л+1.^. = й.Ш+1\ 2 2 2 2 4 v p
3-misol: cos 120° = cos(90° + 30°) = cos90°-cos30°-sin90°-sin30°
0.7Y.I 22
\_ 2’
misol:
cos 15° = cos(45° - 30°) = cos 45° • cos 30° + sin 45° • sin 30° misol:
424з_+4i
2222
tg75° = tg(45° + 30°)
tg45° + tg30° l-tg45°Tg30°
6-misol:
1 +
7з
Уз+i (Уз+i)2 л/3-1 2
3 + 2V3+1 2
tg45°-tg30° l-tg45°Tg30°
l~j
1+1.-L
Уз-i (>/3-i) 3-2V3+1 л/з+1
tgl5° = tg(45° - 30°)
2
2
3. Mustahkamlash. Test yechiladi.
TESTLAR. Agar a=-45° va P=15° boTsa, cos(a+P)+2sinasinP ning qiymatini toping.
A)-I B)^ C)-
VI
D) — 2
E) i 2
3 5л 2. Agar sina = -,sinp =—, -<a va - < p < л boTsa, sin(a-P) ning qiymati qanchaga
teng boTadi ? A)-
16 65
B) — 65
C) — 65 -0
D)-
56 65
E) - — 13
3. Agar tg(a-P)=5 va a=45 boTsa, tgP ning qiymati hisoblang.