Question

Sin40 - cos 70 = root 3 co so 80 prove that

Answer 1

Answer:

Step-by-step explanation:

sinA = sin(180 - A)  

cosA = sin(90 - A)  

sinA - sinB = 2cos((A + B)/2) sin((A - B)/2))  

sinA = -sin(-A)  

cosA = -cos(180 - A)  

cos30 = √3 /2  

sin40 - cos70  

= sin140 - sin20  

= sin140 - sin160  

= 2cos( (140 + 160)/2) sin( (140 - 160)/2 )  

= 2cos150 sin(-10)  

= -2cos150 sin10  

= -2(-cos30) sin10  

= 2cos30 sin10  

= 2cos30 cos80  

= 2(√3 /2) cos80  

= √3 cos80

Answer 2

Answer:

hope it will help you

Step-by-step explanation:

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