How do you use double-angle identities to find the exact value of sin 2x & cos 2x when csc(x) = -25/7 and cos x>0?
1 Answer
Find
Explanation:
As
As
By algebra,
From the triangle, we can find that
The negative sign is because the basic angle is in the third quadrant, where only tangent is positive,
Evaluating
The negative signs are because the angles fall in the third quadrant. Not so sure about that though.