Question 57558

13. Find the exact value of sin 30 ° - sin 45 ° cos 45 ° .
{{{highlight(a)}}}. 0 
b. 1/2 
c. 1 
d. 2 
Here's how:
sin(30)=1/2, sin(45)={{{1/sqrt(2)}}}, cos(45)={{{1/sqrt(2)}}}, therefore,
{{{1/2-(1/sqrt(2))*(1/sqrt(2))}}}
{{{1/2-1/2}}}
{{{0}}}


14. Find the value of tan 42 ° to 4 decimal places.
a. 2.2914 
{{{highlight(b)}}}. 0.9004  Make sure you calculator is on degree mode. 
c. 1.1106 
d. 0.7431 


15. Find the value of sec 38 ° to 4 decimal places.
a. 1.6243 
b. 0.7880 
c. 0.6157 
{{{highlight(d)}}}. 1.2690  
sec(x)=1/cos(x), so if you have a ti-83 type in (cos(38)){{{x^(-1)}}} and it will give you the reciprocal of cos(38) which is sec(38).
Happy Calculating!!!