Respuesta :
Answer: Choice B) cos(69)
Work Shown:
cos(90-x) = sin(x)
cos(90-21) = sin(21)
cos(69) = sin(21)
Work Shown:
cos(90-x) = sin(x)
cos(90-21) = sin(21)
cos(69) = sin(21)
Answer:
B. Cos 69°
Step-by-step explanation:
Given : sin 21°
Solution : To show how Cos 69 ° = Sin 21 °
we will use sine and cosine trigonometric identity
i.e. Cos (90 °-x) = Sin x ---(A)
We are given Sin 21 °
So, putting x =21 ° in (A)
We are getting : Cos(90 °-21 °) = Sin 21 °
⇒Cos 69 ° = Sin 21 °
Hence it is shown that Cos 69 ° = Sin 21 °
