the value of cos 15 is √3+1/2√2
explanation
cos (45-30)
=cos45*cos30+sin45*sin30
=1/√2 * √3/2 + 1/√2 * 1/2
=√6/4 + √2/4
=√6 + √2/4
=√3+1/2√2
Answer:
S=157
Step-by-step explanation:
an= a1+(n-1)d
a2=80+(2-1)(-3)
a2=80-3
a2=77
Sn=(a1+an)*n/2
S2=(80+a2)*2/2
S2=(80+77)*1
S2=157
Here is the solution. Hope it helps.
