Question

помогите срочно
даю 50 баллов
8 класс геометрия
​

Answer 1

Ответ:

1.

$a = 4 \\ \alpha = 30^{\circ} \\ \\ \beta = 90^{\circ} - \alpha = 90^{\circ} - 30^{\circ} = 60^{\circ} \\ \\ \sin( \alpha ) = \frac{a}{c} \\ c = \frac{a}{ \sin( \alpha ) } = \frac{4}{ \sin(30^{\circ} ) } = 4 \times 2 = 8 \\ \\ \cos( \alpha ) = \frac{b}{c} \\ b = c \cos( \alpha ) = 8 \times \frac{ \sqrt{3} }{2} = 4 \sqrt{3}$

2.

1)

$\cos {}^{2} (17^{\circ} ) + \sin {}^{2} (17^{\circ} ) - \sin {}^{2} (60) = \\ = 1 - {( \frac{ \sqrt{3} }{2} )}^{2} = 1 - \frac{3}{4} = 0.25$

2)

$\sin {}^{2} (49) + \cos {}^{2} (49) + \cos {}^{2} (30) = \\ = 1 + {( \frac{ \sqrt{3} }{2} )}^{2} = 1 + \frac{3}{4} = 1.75$

3)

$\sin {}^{2} (30^{\circ} ) + \cos {}^{2} (88^{\circ} ) + \sin {}^{2} (88^{\circ} ) = \\ = {( \frac{1}{2}) }^{2} + 1 = \frac{1}{4} + 1 = 1.25$