Question

please help me solve this.... pleaseeeeeee​

Answer 1

Given that,

cos x = - 4/5

cosine is negative in second and third quadrant but with accordance to given constraints, x would lie in second quadrant where sine is positive.

We know that,

sin²x + cos²x = 1

$\longrightarrow$ sin²x + 16/25 = 1

$\longrightarrow$ sin²x = 9/25

$\longrightarrow$ sin x = 3/5 (Second Quadrant)

Thus,

sin2x

$\longrightarrow$ 2 × 3/5 × -4/5

$\longrightarrow$ -2 × 12/25

$\longrightarrow$ -24/25