Question bank/JEE Main/Mathematics

JEE MainMathematicsEasyLimits, continuity and derivability

In a [IMAGE] ABC, angles A,B,C are in 2: 3: 4
respectively then the cosA is equal to

Show answer and solution
2x + 3x + 4x = 9x = 180º x = 20º
∠A=40∘\angle A = 40^{\circ}
∠B=60∘\angle B = 60^{\circ}
∠C=80∘\angle C = 80^{\circ}
asin⁡40∘=bsin⁡60∘=csin⁡80∘\frac{a}{\sin 40^{\circ}} = \frac{b}{\sin 60^{\circ}} = \frac{c}{\sin 80^{\circ}}
=c2sin40∘cos40∘= \frac{c}{2sin40^{\circ}cos40^{\circ}}

Source: Grass-G / M-11 Mathematics Paper-2 1Nov.docx

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