Question

A expressão séc- 1500° - cossec 990° é:

Answer 1

$sec-1500^{\circ}-cossec~900^{\circ}=$ 

vamos calcular separado

$sec-1500^{\circ}= \frac{1}{cos-1500^{\circ}} = \frac{1}{cos-60^{\circ}} = \frac{1}{ \frac{1}{2} } =2 \\ \\ cos-1500^{\circ}=1500\div360=4~voltas~de~360~-60 \\ \\ como~cos-60^{\circ}~est\acute a~~no~quuarto~qudrante=+ \frac{1}{2}$ 

$cossec~990^{\circ}= \frac{1}{sen~990^{\circ}} = \frac{1}{sen~270^{\circ}} = \frac{1}{-1} =-1 \\ \\ sen990^\circ}=990\div360=2~voltas~de~360~+270 \\ sen270^{\circ}=-1$

vamos calcular

$sec-1500^{\circ}-cossec~990^{\circ}= \\ \\ 2+1=3\mapsto~letra~~C$