Answer 21 and 22 with a brief explanation 20.4 21. If cos A = tan B, cos

Answer 21 and 22 with a brief explanation

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20.4 21. If cos A = tan B, cos B = tan Cand cos C = tan A, Then sinA = 1. 2 sin 18° 2. 2 sin 36° 3. 2 cos36° 4. 2 cos18° 21.1 cos A = tan B, cos?A = tan?B, cos?A = sec?B – 1, = cos? A = cot² C – 1 cos B = tan C cos²B = tan?C sec2 B = cot? C cos? C- sin? c 2 cos? C-1 = cos? A = sin? c 1- cos? c 2 tan? A – 1 = cos?A = {:: cos? C = tan2² A} %3D 1- tan? A 2sin? A - cos? A = 1- sin?A %3D cos? A – sin? A 3 sin? A -1 1-2 sin? A = (1– sin? A) = %3D 22. = sin e (sin e + sin 30). Then f(0) : Let f(0) (A) > 0 only when e 20 (B) < 0 for all real e (C) 2 0 for all real e (D)<0 only when 0s0. 22.A 4 V Edit with WPS Office Mathematics Trigonometry 20.4 21. If cos A = tan B, cos B = tan Cand cos C = tan A, Then sinA = 1. 2 sin 18° 2. 2 sin 36° 3. 2 cos36° 4. 2 cos18° 21.1 cos A = tan B, cos?A = tan?B, cos?A = sec?B – 1, = cos? A = cot² C – 1 cos B = tan C cos²B = tan?C sec2 B = cot? C cos? C- sin? c 2 cos? C-1 = cos? A = sin? c 1- cos? c 2 tan? A – 1 = cos?A = {:: cos? C = tan2² A} %3D 1- tan? A 2sin? A - cos? A = 1- sin?A %3D cos? A – sin? A 3 sin? A -1 1-2 sin? A = (1– sin? A) = %3D 22. = sin e (sin e + sin 30). Then f(0) : Let f(0) (A) > 0 only when e 20 (B) < 0 for all real e (C) 2 0 for all real e (D)<0 only when 0s0. 22.A 4 V Edit with WPS Office Mathematics Trigonometry