Question

given that sinA= 1/2 and cos B= 1/2 then value of cos (a+b) is
a. 0
b. 1
c. 1/root 3
d. root 3/2


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Answer 1

Answer:

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Step-by-step explanation:

Given :

$sinA = \frac{1}{2} \\ we \: know \: that \: sin \: 45° = \frac{1}{2} \\ A = 45° \\ cos \: B = \frac{1}{2} \\ we \: know \: that \: cos \: 60° = \frac{1}{2} \\ then \: B \: = 60°$

Find :-

$\cos(A+B) = \cos(45°+60°) \\ \ = > cos(90°) \\ we \: know \: that \: \cos(90°) = 0 \\ \cos(A+B) = 0$

Option A is the correct answer