Maths 3u trig
posted by Jenny on .
If sinA = 1/3 and cosA<0
find the exact value of tan2A

sinA = 1/3 and cosA<0
find the exact value of tan2A
What quadrant is A? Sin is +, cos is  so quadrant 2, so 2 A is quadrant 3 or 4
cos^2A = 1  sin^2A = 11/9 = 8/9
cos A = (2/3)sqrt 2
tanA = (1/3)/[(2/3)sqrt2)] = 1/(2 sqrt 2)
tan 2A = 2 [1/(2 sqrt 2)]/[1 1/8]