Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class


Example 17 Discuss the continuity of sine function.Let 𝑓(π‘₯)=sin⁑π‘₯ Let’s check continuity of f(x) at any real number Let c be any real number. We know that A function is continuous at π‘₯ = 𝑐 if L.H.L = R.H.L = 𝒇(𝒄) i.e. lim┬(x→𝑐^βˆ’ ) 𝑓(π‘₯)= lim┬(x→𝑐^+ ) " " 𝑓(π‘₯)= 𝑓(𝑐) LHL at x β†’ c lim┬(x→𝑐^βˆ’ ) f(x) = lim┬(hβ†’0) f(c βˆ’ h) = (π‘™π‘–π‘š)┬(β„Žβ†’0) sin⁑〖(π‘γ€—βˆ’β„Ž) = (π‘™π‘–π‘š)┬(β„Žβ†’0) (sin⁑𝑐 cosβ‘β„Ž "βˆ’ cos c sin h " ) = (sin⁑𝑐 cos⁑0 "βˆ’ cos c sin 0" ) = sin⁑𝑐× 1"βˆ’ cos c" Γ— 0 = sin c RHL at x β†’ c lim┬(x→𝑐^+ ) f(x) = lim┬(hβ†’0) f(c + h) = (π‘™π‘–π‘š)┬(β„Žβ†’0) sin⁑〖(𝑐〗+β„Ž) = (π‘™π‘–π‘š)┬(β„Žβ†’0) (sin⁑𝑐 cosβ‘β„Ž "+ cos c sin h " ) = (sin⁑𝑐 cos⁑0 "+ cos c sin 0" ) = sin⁑𝑐× 1" + cos c" Γ— 0 = sin c sin⁑(π‘₯βˆ’π‘¦) =sin⁑π‘₯ cosβ‘π‘¦βˆ’cos⁑π‘₯ sin⁑𝑦 sin⁑(π‘₯+𝑦) =sin⁑π‘₯ cos⁑𝑦+cos⁑π‘₯ sin⁑𝑦 𝐴𝑠, cos⁑0=1 & sin⁑0=0 𝐴𝑠, cos⁑0=1 & sin⁑0=0 And, 𝒇(𝒄) = π’”π’Šπ’β‘π’„ Since L.H.L = R.H.L = 𝑓(𝑐) Therefore, 𝑓(π‘₯) is continuous for all real number So, π’”π’Šπ’β‘π’™ is continuous.

Ask a doubt
Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.