Question

Тригонометрия помогите​

Answer 1

Ответ:

B

Пошаговое объяснение:

(1-sin²178/cos²178)/(sin²178/cos²178 +1)= (cos²178-sin²178)/cos²178 : (sin²178+cos²178)/cos²178= (cos²178-sin²178)/cos²178*cos²178/1= cos²178-sin²178= cos356= cos4

cos4=2cos²2-1

2m²-1

Answer 2

$\dfrac{1 - \text{tg}^{2} 178^{\circ}}{\text{tg}^{2} 178^{\circ} + 1} = \dfrac{1 - \text{tg}^{2} (180^{\circ} - 2^{\circ})}{\text{tg}^{2} (180^{\circ} - 2^{\circ}) + 1} = \dfrac{1 - \text{tg}^{2} 2^{\circ}}{\text{tg}^{2} 2^{\circ} + 1} = \dfrac{1 - \left(\dfrac{\sin 2^{\circ}}{\cos 2^{\circ}} \right)^{2}}{\left(\dfrac{\sin 2^{\circ}}{\cos 2^{\circ}} \right)^{2} + 1} =$

$= \dfrac{1 - \dfrac{\sin^{2} 2^{\circ}}{\cos^{2} 2^{\circ}}}{\dfrac{\sin^{2} 2^{\circ}}{\cos^{2} 2^{\circ}} + 1} = \dfrac{\dfrac{\cos^{2} 2^{\circ} - \sin^{2}2^{\circ}}{\cos^{2}2^{\circ}} }{\dfrac{\sin^{2}2^{\circ} + \cos^{2}2^{\circ}}{\cos^{2}2^{\circ}} } = \dfrac{\cos^{2}2^{\circ} - (1 - \cos^{2}2^{\circ})}{1} =$

$= 2\cos^{2}2^{\circ} - 1$

Если $m = \cos 2^{\circ}$, то $\dfrac{1 - \text{tg}^{2} 178^{\circ}}{\text{tg}^{2} 178^{\circ} + 1} =2m^{2} - 1$

Ответ: $\text{B}) \ 2m^{2} - 1$