Question

If A = B = 60°. Verify the Cos (A – B) = Cos A cos B + sin A sin B

Answer 1

A=B=60
then A=60
B=60
then
cos(A-B)=cosAcosB+sinAsinB
cos(60-60)=cos60cos60+sin60sin60
cos0=cso60cos60+sin60sin60
(we know that
$cos0 = 1 \\ cos60 = 1 \div 2 \\ sin60 = \sqrt{3} \div 2 \\ from \: the \: trigonometry \: table$
$1 = {1 \div 2 \times 1 \div 2} + { \sqrt{3 \div } \div 2 \times \sqrt{3} \div 2} \\ 1 = 1 \div 4 + 3 \div 4 \\ 1 = 4 \div 4 \\ 1 = 1$

Answer 2

Answer:

Step-by-step explanation:

A=B=60

then A=60

B=60

then

cos(A-B)=cosAcosB+sinAsinB

cos(60-60)=cos60cos60+sin60sin60

cos0=cso60cos60+sin60sin60

(we know that

cos0 = 1 \\ cos60 = 1 \div 2 \\ sin60 = \sqrt{3} \div 2 \\ from \: the \: trigonometry \: table

1 = {1 \div 2 \times 1 \div 2} + { \sqrt{3 \div } \div 2 \times \sqrt{3} \div 2} \\ 1 = 1 \div 4 + 3 \div 4 \\ 1 = 4 \div 4 \\

1 = 1