Question
Mathematics Question on Trigonometry
If Sin A : Cos A = 4 : 7 , then the value of (7sinA+2cosA)(7sinA−3cosA) is
A
143
B
23
C
31
D
61
Answer
61
Explanation
Solution
Assume sinA=4and cosA=7
The expression given in the question, = 7 sinA+2 cosA7 sinA−3 cosA
From the equation we get = 7(4)+2(7)7(4)−3(7)
= 427 = 61
The correct option is (D): 61