Find the EXACT value of sin(2A) if cscA=5/4

Question

Assume A is a Quadrant I angle in standard position.
sin(2A+=

Answer 1

draw a triangle that fits the condition.
cscA = 5/4 means
sinA = 4/5
cosA = 3/5
Now, recall your double-angle formula
sin(2A) = 2 sinA cosA
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