Question

SOS
Can your help me?

Answer 1

Ответ:

Пошаговое объяснение:

1) а) cos(5,4)*sin(13) = cos(5,4-6,28)*sin(13-12,56) = cos(-0,88)*sin(0,44) =

= cos(0,88)*sin(0,44) > 0

Оба множителя, очевидно, > 0

б) tg(9π/7)*cos(14π/9) = tg(π+2π/7)*cos(2π-4π/9) = tg(2π/7)*cos(-4π/9) =

= tg(2π/7)*cos(4π/9) > 0

Оба множителя > 0

в) ctg(613°)*tg(1920°) = ctg(3*180°+73°)*tg(10*180°+120°) =

= ctg(73°)*tg(120°) < 0

ctg(73°) > 0; tg(120°) < 0.

2) а) tg(3π/4) + sin(-2π/3) + cos(11π/6) = -1 - √3/2 + √3/2 = -1

б) 4cos^2(π/11) + 4sin^2(π/11) - 3tg(π/5)*ctg(π/5) = 4(cos^2(π/11) + sin^2(π/11) - 3*1 =

= 4*1 - 3 = 1

3) а) (1 - sin^2 t)/cos^2 t + tg^2 t = 1/cos^2 t - tg^2 t + tg^2 t = 1/cos^2 t

б) [sin(π+t)*sin(2π+t)] / [tg(π+t)*cos(3π/2+t)] =

= (-sin t*sin t) / (tg t*(-sin t)) = sin t/tg t = cos t

4) cos a = 5/13; 0 < a < π/2

sin a > 0; cos a > 0

sin^2 a = 1 - cos^2 a = 1 - 25/169 = 144/169

sin a = 12/13

tg a = sin a / cos a = (12/13) : (5/13) = 12/5

ctg a = 1/tg a = 5/12

5) График сами стройте, я в телефоне его построить не могу.