L lolitaaa Active Member Joined Dec 28, 2013 Messages 258 Location QVB Gender Female HSC 2014 May 6, 2014 #1 How do you do sin(cos^-1 (-15/17)) ? Thanks a lot!!
D Drongoski Well-Known Member Joined Feb 22, 2009 Messages 4,234 Gender Male HSC N/A May 6, 2014 #2 Draw a right-angled triangle, with sides: 8, 15, 17 cos^-1 (-15/17)) is in the 2nd quadrant. Looking at the triangle, the sine of this angle is + 8/17 (sine of the angle in the 2nd Quadrant is +ve) So answer is: 8/17 ps: didn't you complete your HSC last year?
Draw a right-angled triangle, with sides: 8, 15, 17 cos^-1 (-15/17)) is in the 2nd quadrant. Looking at the triangle, the sine of this angle is + 8/17 (sine of the angle in the 2nd Quadrant is +ve) So answer is: 8/17 ps: didn't you complete your HSC last year?
B braintic Well-Known Member Joined Jan 20, 2011 Messages 2,111 Gender Undisclosed HSC N/A May 6, 2014 #3 Alternatively: Use the rule cos^-1 (-x) = pi - cos^-1 (x) sin(cos^-1 (-15/17)) = sin (pi - cos^-1 (15/17)) = sin (cos^-1 (15/17)) [second quadrant angle] THEN use your right-angled triangle to get 8/17
Alternatively: Use the rule cos^-1 (-x) = pi - cos^-1 (x) sin(cos^-1 (-15/17)) = sin (pi - cos^-1 (15/17)) = sin (cos^-1 (15/17)) [second quadrant angle] THEN use your right-angled triangle to get 8/17
