Ex 8.1, 1 - Chapter 8 Class 10 Introduction to Trignometry

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Ex 8.1, 1 In Δ ABC, right-angled at B, AB = 24 cm, BC = 7 cm. Determine : sin A, cos A Step1 : Finding sides of triangle In right triangle ABC, Using Pythagoras theorem (Hypotenuse)2 = (Height)2 + (Base)2 AC2 = AB2 + BC2 AC2 = 242 + 72 AC2 = 576 + 49 AC2 = 625 AC = √𝟔𝟐𝟓 AC = √(25^2 ) AC = 25 Hence AC = 25 cm Step 2: Finding sin A , cos A sin A = (𝑠𝑖𝑑𝑒 𝑜𝑝𝑝𝑜𝑠𝑖𝑡𝑒 𝑡𝑜 ∠ 𝐴)/𝐻𝑦𝑝𝑜𝑡𝑒𝑛𝑢𝑠𝑒 = 𝐵𝐶/𝐴𝐶 = 𝟕/𝟐𝟓 cos A = (𝑠𝑖𝑑𝑒 𝑎𝑑𝑗𝑎𝑐𝑒𝑛𝑡 𝑡𝑜 ∠ 𝐴)/𝐻𝑦𝑝𝑜𝑡𝑒𝑛𝑢𝑠𝑒 = 𝐴𝐵/𝐴𝐶 = 𝟐𝟒/𝟐𝟓 Ex 8.1, 1 In Δ ABC, right-angled at B, AB = 24 cm, BC = 7 cm. Determine : (ii) sin C, cos C Now, AC = 25 cm, AB = 24 cm, BC = 7 cm sin C = (𝑠𝑖𝑑𝑒 𝑜𝑝𝑝𝑜𝑠𝑖𝑡𝑒 𝑡𝑜 ∠ 𝐶)/𝐻𝑦𝑝𝑜𝑡𝑒𝑛𝑢𝑠𝑒 = 𝐴𝐵/𝐴𝐶 = 𝟐𝟒/𝟐𝟓 cos C = (𝑠𝑖𝑑𝑒 𝑎𝑑𝑗𝑎𝑐𝑒𝑛𝑡 𝑡𝑜 ∠ 𝐶)/𝐻𝑦𝑝𝑜𝑡𝑒𝑛𝑢𝑠𝑒 = 𝐵𝐶/𝐴𝐶 = 𝟕/𝟐𝟓