Class 10 NCERT Introduction to Trigonometry

NCERT

Class 10 NCERT

1.   1- In $\Delta$ABC right angled at B, AB = 24 cm, BC = 7 m. Determine$\\$ (i) sin A, cos A$\\$ (ii) sin C, cos C

Applying Pythagoras theorem for $\Delta$ABC, we obtain$\\$ $AC^2 = AB^2 + BC^2$$\\$= $(24 cm)^2 + (7 cm)^2$$\\$ = $(576 + 49) cm^2$$\\$ = $625 cm^2$$\\$$\therefore AC = \sqrt{625} cm = 25 cm$$\\$

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$(i) sin A = \dfrac{side opposite to \angle A}{Hypotenuse} = \dfrac{BC}{AC}$$\\$$=\dfrac{7}{25}$$\\$$(ii) cos A = \dfrac{side adjacent to \angle A}{Hypotenuse} = \dfrac{AB}{AC} = \dfrac{24}{25}$$\\$ figure