Can someone help me answer this question? 'find the exact value of Cos theta, given sin theta = 5/9 and cos theta < 0
3 Answers
I got
Explanation:
Have a look:
= -0.8315 (4dp)
Explanation:
Find
The sin will also have the value
If you are not sure which of these angles will have cos < 1, try both.
(note that the numbers for both angles are actually the same but one is positive and the other is negative)
(so
Explanation:
#"using the "color(blue)"trigonometric identity"#
#•color(white)(x)sin^2theta+cos^2theta=1#
#rArrcostheta=+-sqrt(1-sin^2theta)#
#"given "sintheta=5/9" and "costheta<0#
#"then "theta" is in the second quadrant"#
#costheta=-sqrt(1-(5/9)^2)#
#color(white)(costheta)=-sqrt(1-25/81)#
#color(white)(costheta)=-sqrt(56/81)=-sqrt56/9#