cosA < 0. ∴ cos A = `- 4/5` sin B = `4/5` We know that, cos 2 B = 1 – sin 2 B = `1 - (4/5)^2` = `1 - 16/25 = 9/25` ∴ cos B = `± 3/5` Since B lies in the second quadrant. cos B < 0. ∴ cos B = `-3/5` ∴ 4cos A + 3cos B = `4(-4/5) + 3(-3/5)` = `-16/5 - 9/5` = `-25/5` = – 5.
>>Class 11>>Maths>>Trigonometric Functions>>Trigonometric Functions of Sum and Difference of Two angles>>If cos A = 4/5 , cos B = 12/13 , 3pi/Open in AppUpdated on 2022-09-05SolutionVerified by TopprA and B both lie in the IV quadrant.=> are negativei iiSolve any question of Trigonometric Functions with-Was this answer helpful? 00More From ChapterLearn with Videos Practice more questions
Pada soal diketahui sin A = 5 4 dan cos B = 13 5 untuk A sudut tumpul dan B sudut lancip. Sehingga sudut A berada pada kuadran II sedangkan sudut B berada pada kuadran I. Sehingga untuk cos A bernilai negatif: sin A sisi miring sisi depan = = → → 5 4 5 4 sisi depan = 4 sisi miring = 5Open in Appwe have the value of and but we don't have the value of and so, first we find the value of and let side opposite to angle hypotenuse where is any positive integer So, by Pythagoras theorem we can find the third side of a triangle taking positive square root as side cannot be negative So, Base we know that side adjacent to angle hypotenuse so, now we have to find the we know that let side adjacent to angle hypotenuse where is any positive integer so, by Pythagoras theorem, we can find the third side of a triangle taking positive square root since, side cannot be negative so, perpendicular we know that Now putting the values, we get Was this answer helpful? 00
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