OG详解-OG10 数学2 Q15

Choice B is correct. The sine of any acute angle is equal to the cosine of its complement. It’s given that in right triangle RST, the sum of the measures of angle R and angle S is 90 degrees. Therefore, angle R and angle S are complementary, and the value of sinR is equal to the value of cosS. It’s given that the value of sin R is √154​​ , so the value of cosS is also  √154​​.
Choice A is incorrect. This is the value of tanS. Choice C is incorrect. This is the value of  1cosS​​ . Choice D is incorrect. This is the value of  1tan​S​ .