If sin (π / 4 + α) = m, find the value of COS (π / 4 - α)

If sin (π / 4 + α) = m, find the value of COS (π / 4 - α)

cos(π/4-α)
=sin[π/2-(π/4-α)]
=sin(π/4 +α)
=m

Given that sin α + cos α = 4 / 3 (0 ＜ α ＜ π / 4), the value of sin α - cos α is

Sin α + cos α = 4 / 3 (sin α + cos α) & # 178; = 1 + 2sinacosa = 16 / 9  2sinacosa = 7 / 9  (0 ﹤ α ﹤ π / 4)  sin Cosa ﹤ 0  sin cosa = - √ (sin COSA) & # 178; = - √ (1-7 / 9) = - √ 2 / 3, please click [satisfactory answer]; if you are not satisfied

It is known that sin θ + cos θ = 4 / 3 (0

(sinθ+cosθ)²=16/9
sinθ²+cosθ²+2sinθcosθ=16/9
2sinθcosθ=7/9
Sin θ - cos θ = under radical (sin θ - cos θ) & sup2; = under radical (1-7 / 9) = (radical 2) / 3 (π / 4