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Question Number 134538 by bemath last updated on 05/Mar/21

How do you find the interval in which x belongs such that |sinx+cosx|=sinx + cosx?\n

Answered by EDWIN88 last updated on 05/Mar/21

 let sin x+cos x = y ⇒we get equation ∣y∣ = y   this equation satisfied if only if y≥0  since sin x+cos x = (√2) sin (x+(π/4)) we get  ⇒(√2) sin (x+(π/4)) ≥ 0 , sin (x+(π/4))≥ 0  note that sine function be ≥ 0 in first and   2^(nd)  quadrant so 0 ≤ x+(π/4)≤π ; or   −(π/4)+2kπ≤x≤((3π)/4) +2kπ.

letsinx+cosx=ywegetequationy=y thisequationsatisfiedifonlyify0 Extra close brace or missing open brace Extra close brace or missing open brace notethatsinefunctionbe0infirstand 2ndquadrantso0x+π4π;or π4+2kπx3π4+2kπ.

Commented byEDWIN88 last updated on 05/Mar/21

Commented byEDWIN88 last updated on 05/Mar/21

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