When sum of two angles is 90°, then each of those two angles will be considered to be the complementary angle of each other.Example : 60° and 30° are two angles, and their sum is 90°. So, 60° and 30° are complementary angles.
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[tex] \bf{\underline{\underline{\dag According\ to\ the\ question:-}}} [/tex]
[tex]\qquad[/tex][tex] \pink{\bf\longrightarrow {x\ +\ x\ +\ 13.8°\ =\ 90⁰} }[/tex]
[tex]\qquad[/tex][tex] \sf \longrightarrow 2x + 13.8° = 90° [/tex]
[tex]\qquad[/tex][tex] \sf \longrightarrow 2x = 90° - 13.8° [/tex]
[tex]\qquad[/tex][tex] \sf \longrightarrow 2x = 76.2° [/tex]
[tex]\qquad[/tex][tex] \sf \longrightarrow x = \cancel{\dfrac{76.2°}{2}} [/tex]
[tex]\qquad[/tex][tex] \pink{\bf \longrightarrow x = 38.1° }[/tex]
Then –
[tex]\qquad[/tex][tex] \bf \longrightarrow x +13.8° [/tex]
[tex]\qquad[/tex][tex] \tt \longrightarrow 38.1° + 13.8° [/tex]
[tex]\qquad[/tex][tex] \tt \longrightarrow 51.9° [/tex]
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